Free Technical Software

GPU / Open CL vs. CPU performance

Fri, 25 Feb 2022 00:00:00 GMT

All massive data processing applications can benefit from the ever-increasing processing capacity of modern computers, which is now affordable for anyone's pocket. I will show in this article a basic performance comparison among various CPU / GPU platforms, based on the well-known Mandelbrot set and its surprising graphical representation.

Training sparring robot III

Thu, 28 Jan 2021 00:00:00 GMT

This article is the last in the series dedicated to building the Octopussy martial arts and self-defence training sparring robot. Here, I will explain the use of the software to control the device, which allows you to design a virtually unlimited range of training routines within the robot's features.

Training sparring robot II

Wed, 27 Jan 2021 00:00:00 GMT

This article is the second one on the Octopussy training sparring robot for self-defence and martial arts. Here, I will explain how to build the electronics of the invention. The task consists of little more than connecting a few wires, although a tin soldering iron would also be convenient to have at hand to finish the job better.

Training sparring robot I

Mon, 25 Jan 2021 00:00:00 GMT

I will show in this series of articles how to build a self-defence and martial arts training robot. I have named Octopussy to the invention since you can put several limbs to simulate different types of punches and kicks directed to all of the body parts. It is controlled by a computer, an Arduino board, and an application. I also provide the application source code for you to make modifications as you want.

Chess match database manager VI

Thu, 31 Dec 2020 00:00:00 GMT

I finish the series dedicated to the ChessPosDB chess match database manager with this article. In this post, I will explain how to install and configure the database server used with the application, which can be Oracle, MySQL, or SQL Server. Whichever database server you choose, you can install it on the same computer as the application or on another more powerful computer that you can access through your local network.

Chess match database manager V

Mon, 28 Dec 2020 00:00:00 GMT

This post is the fifth in a series of articles about the ChessPosDB application, which allows you to store many chess games in different professional database engines and search for them with a wide variety of options. Here, I will show how to query the database with the filters explained in the previous ones. We will also see the chess match editing options, which allow adding comments and new tags.

Chess match database manager IV

Thu, 24 Dec 2020 00:00:00 GMT

This article is the fourth of a series of articles dedicated to the ChessPosDB application, a chess game database manager with a powerful search engine. Here, I will finish the section about the search filters by showing the chess match filters. Those filters can include several movement or position filters, which we have already seen in previous posts.

Chess match database manager III

Mon, 21 Dec 2020 00:00:00 GMT

This post is the third of the series of articles about the ChessPosDB database manager application. Here you also have a link to the first article in this series, in case you want to start reading from the beginning. In the present article, I will continue commenting on the rest of the movement and position filters that can be applied to find chess games in the database. As you may recall from the previous article, we can combine these filters in multiple ways to build virtually any query that you can think of.

Chess match database manager II

Thu, 17 Dec 2020 00:00:00 GMT

In this series of articles, I will comment on a chess game database manager, ChesPosDb. In the first article in this series, I explained how to load chess games in the database using PGN files, which you can download from many Internet sites. In this article and the following ones, I will show the different filter types that you can build to search chess matches in the database.

Chess match database manager I

Sat, 12 Dec 2020 00:00:00 GMT

In this series of articles, I will present an application to manage a chess match database, ChesPosDb. It is not a program that plays chess; it only stores matches, but it allows queries with a large number of options: searching for games in which a series of moves occur, either one after another or separated by several moves, and even look for partially defined positions, no matter in which place on the board the pieces are located.

Time series, RQA and neural networks II

Thu, 18 Jul 2019 00:00:00 GMT

In this second article in the series on combining recurrence quantification analysis (RQA) and neural networks to work with complex time series, we will examine some ideas about possible processing that you can apply to the data and the selection of parameters. We will work using electrocardiographic signals, as mentioned in the previous article.

Time series, RQA and neural networks I

Tue, 11 Jun 2019 00:00:00 GMT

In some other articles in this blog, I have already written about complex time series, recurrence quantification analysis (RQA) and neural networks. In this series of articles, I will discuss some points to take into account when combining the use of these two tools to identify patterns in complex series, such as detecting anomalies in electrocardiograms or electroencephalograms.

EDF files of physiological signals

Thu, 28 Mar 2019 00:00:00 GMT

When we try to learn how to work with time series, it is very useful to have good data sets, and much better if they contain real data. It is difficult to obtain long series, or series presenting interesting and well located and identified patterns, with which we can perform practices. An excellent source of complex time series is our own organism, and everything we can learn by working with them can be extrapolated to any other context.

Neural networks and genetic algorithms III

Mon, 18 Mar 2019 00:00:00 GMT

With this article I conclude the series dedicated to the application of genetic algorithms to the design of neural networks. I will explain the most relevant code of the sample application given with these articles, mainly the classes dedicated to the genes management and the selection process. You can find more information in the previous articles of the series.

Neural networks and genetic algorithms II

Thu, 28 Feb 2019 00:00:00 GMT

In this second article on the application of evolutionary algorithms to the optimization of the design of neural networks, I am going to provide a small sample application that allows you to build and train networks, in addition to using this type of algorithms to find the best configuration for a given data set. The application allows generating artificial test data, and I provide the source code for you to be able to modify it, as you want.

Neural networks and genetic algorithms I

Fri, 22 Feb 2019 00:00:00 GMT

When we try to apply a neural network to a given problem, finding the most suitable topology for it can be a tedious trial and error task, as well as end up producing a poorly optimized network. To automate this process, we can draw on evolutionary algorithms, inspired in the natural selection of living organisms, which can greatly facilitate our job.

The back propagation algorithm

Sun, 02 Dec 2018 00:00:00 GMT

One of the most popular algorithms for training multilayer artificial neural networks is the back propagation algorithm, or retro-propagation algorithm. In this article I will try to explain its fundamentals, through a simplified implementation of a neural network that allows testing with different configurations of the network.

Posture recognition with Kinect V

Mon, 23 Jul 2018 00:00:00 GMT

This article closes the series on posture recognition using the Microsoft Kinect sensor. To finish, I will simply show you the implementation of a basic form that uses the class libraries explained in the previous articles.

Posture recognition with Kinect IV

Mon, 04 Jun 2018 00:00:00 GMT

We continue with the series about posture recognition with the Microsoft Kinect sensor. This time I will comment the classes responsible of posture normalization of the body in the way commented in the first article, so that we obtain a series of data that constitute a simplified version of the skeleton most appropriate for analysis using pattern recognition techniques.

Posture recognition with Kinect III

Sun, 13 May 2018 00:00:00 GMT

In the previous article of this series I showed the structures, enumerations and classes that the application uses to be independent of the sensor version and the Kinect SDK. In this third article I will show a possible implementation of a class that deals with reading and converting the skeletons using version 2.0 of the SDK, for the Xbox One sensor.

Posture recognition with Kinect II

Sat, 05 May 2018 00:00:00 GMT

In this second article in the series about recognition of postures using the Microsoft Kinect sensor I will show generic classes and structs used to isolate the application from the different versions of the SDK. The version of the SDK that we must use depends on the sensor model that we have. In the example code I have used version 2.0, for the Xbox One sensor.

Posture recognition with Kinect I

Sun, 22 Apr 2018 00:00:00 GMT

One of the most interesting features offered by the Microsoft Kinect sensor is human bodies detection, which allows us to develop applications based on the different positions of the user's body and that can be handled remotely using those positions. To do this, it provides a series of points that represent the different joints of the body.

Homemade surveillance using Kinect

Sun, 11 Mar 2018 00:00:00 GMT

In previous articles I presented a home video surveillance system, the ThiefWatcher application. It is an extensible application that works combining several protocols, such as cameras, triggers, communication channels and storage systems. In this article I will show how to implement some of these protocols using the Microsoft Kinect sensor.

Basic image capturing with Kinect

Sun, 18 Feb 2018 00:00:00 GMT

The Microsoft Kinect sensor is a very powerful device that provides image capturing, distance measurement and body postures and facial expressions recognition services, which makes it suitable for infinity of applications. In this introductory article I will show how to use it to capture different types of images.

Solving a Sudoku as an optimization problem

Sun, 10 Dec 2017 00:00:00 GMT

Solving any Sudoku is a problem that can seem complicated if brute force methods are used, testing each and every one of the possible combinations. But, with the right approach, any of these problems can be solved in a few milliseconds. In this article, I will show you a way to achieve it through an optimized method.

Multitasking V, asynchronous programming with async and await

Sat, 02 Dec 2017 00:00:00 GMT

To conclude this series about programming multitasking applications, I will show the use of a simple mechanism that allows implementing asynchronous methods whose waiting times are used for the execution of other parallel tasks or events triggered by user interface controls.

Multitasking IV, interacting with Windows UI

Sat, 18 Nov 2017 00:00:00 GMT

So far I have shown examples of multitasking that block the application until they finished. This is not very useful in practice. Usually, we want that the user can continue interacting with the application while the tasks are running in the background; we could want also the threads to interact with the user interface.

Multitasking III, concurrent access

Sun, 05 Nov 2017 00:00:00 GMT

In multitasking applications there is a problem when concurrent access to resources, such as files or memory, when you launch several tasks at once. Two tasks cannot write at the same time in the same memory address, it is required to make sure that some data is not modified while we are reading them or things like that. In this article I will review the tools provided by .NET Framework to deal with these issues.

Multitasking II, Synchronizing Tasks

Tue, 19 Sep 2017 00:00:00 GMT

After reviewing the classes to implement the basic multitasking, in this article I will review different mechanisms that allow a synchronization between various tasks, all of them defined in the System.Threading namespace, with which you can organize the work when the Interactions between tasks require a particular order.

Multitasking I, basic classes

Mon, 04 Sep 2017 00:00:00 GMT

With this article begins a series in which I will review the basic mechanisms provided by the .NET Framework for the implementation of multitasking applications. First of all I will show the basic classes that allow you to launch multiple processes and make a performance comparison between them.

The importance of having a good log

Fri, 14 Jul 2017 00:00:00 GMT

We often neglect, due to lack of time, inexperience or simple laziness, to provide our developments with good mechanisms to trace the activity, which results in a substantial increase in the difficulty and time needed to determine the causes of certain errors that aren't detected in the moment they happen, but when the state of the system may have changed substantially.

Cellular automata, WInCA application VIII

Fri, 23 Jun 2017 00:00:00 GMT

This is the last article of the series dedicated to the WinCA application. This application allows the edition and to execution of cellular automata. To finish, I will review the code that implements the automaton itself, using all the classes and interfaces explained in the previous articles.

Cellular automata, WInCA application VII

Fri, 02 Jun 2017 00:00:00 GMT

I continue explaining the basics of the WinCA application code, dedicated to the designing and execution of cellular automata. This time I will tell you about the implementation of the cells and other auxiliary classes needed to build and execute automata.

Cellular automata, WinCA application VI

Fri, 26 May 2017 00:00:00 GMT

We continue with the series dedicated to cellular automata and the WinCA application, dedicated to build and executing them. In this article I will explain the code related to the expression system that allows establishing the conditions to change from one state to another.

Cellular automata, WinCA application V

Fri, 19 May 2017 00:00:00 GMT

I continue to comment on the source code of the WinCA program, dedicated to cellular automata. In this article I will explain the interfaces and classes with which cell states are implemented and their edition. You can use these interfaces and classes as a basis to extend the application features.

Cellular automata, WinCA application IV

Fri, 12 May 2017 00:00:00 GMT

Once reviewed the operation of the WinCA application, dedicated to cellular automata, let's see how the source code is organized. In this article I will explain the properties of cell states, and how they can be extended to add new functionalities by implementing new classes with the corresponding interfaces.

Cellular automata, WinCA application III

Fri, 05 May 2017 00:00:00 GMT

In this article, third of the series, I continue to explain the operation of the WinCA application, devoted to the construction and execution of cellular automata. This time I will show the language used to define the transitions between the different states of the automaton cells.

Cellular automata, WinCA application II

Fri, 28 Apr 2017 00:00:00 GMT

This is the second article in the series about the WinCA application, dedicated to the construction and execution of cellular automata. In this article I will show how to design the diferent states that can have the automaton cells, and the properties that can be assigned to them, using the application editors.

Cellular automata, WinCA application I

Fri, 21 Apr 2017 00:00:00 GMT

Cellular automata are mathematical models used to study the evolution of complex dynamic systems by simulating the interactions over time of a large number of elements, called cells. In this series of articles I will present the WinCA application, with which you can build and run this type of objects.

Using the Dropbox API from a Xamarin Forms PCL App

Fri, 24 Mar 2017 00:00:00 GMT

Dropbox is one of the most popular applications for sharing and storing files in the cloud. In a desktop computer it is very easy to use it, since it is integrated into the file system and the folders are just like any other folder in the system, so that they can be managed using the usual file management API. From a mobile device, however, it is necessary to use the Dropbox API to manage and access the files. In this article I will show you how to use it in a PCL Xamarin Forms application.

ThiefWatcher, a homemade indoor surveillance system III

Fri, 17 Mar 2017 00:00:00 GMT

With this article I finish the series dedicated to the ThiefWatcher solution, a homemade video surveillance system that is triggered when some intruder enter your home, alerts you by calling to the mobile phone and allows you to obtain at the moment pictures that you can use to help the police quickly identify the thieves and increase the chances of quickly recovering your stolen belongings. In this last article I will explain the App that is used as a remote client of the system.

ThiefWatcher, a homemade indoor surveillance system II

Fri, 10 Mar 2017 00:00:00 GMT

In this second article in the series on the ThiefWatcher homemade video surveillance system, I will explain the different protocols that the application uses to interact with its different components, which can be replaced by different new ones allowing a large number of combinations. There is a protocol to communicate with the camera, another to trigger the system, another to alerting the user remotely, and, finally, a protocol to exchange photographs and messages to manage the server from client devices.

ThiefWatcher, a homemade indoor surveillance system I

Fri, 03 Mar 2017 00:00:00 GMT

In this series of articles I will do a bit of DIY to build a video surveillance and alarm system against home thefts, using relatively cheap materials and a program that will notify to your mobile phone in case of detecting intruders and allow you to take photographs of them to be able to immediately notify the police and provide them those photos. Rapid identification of thieves can be crucial for you to recover all our possessions quickly.

Create a simple WCF connector for DBTextFinder

Fri, 03 Feb 2017 00:00:00 GMT

WCF (Windows Communication Foundation) is a framework for creating distributed applications whose components communicate with each other through services, using a wide range of network protocols. In this article I will comment on the fundamentals of creating and configuring one of these services through a data connector for the DBTextFinder application, a program to search for texts in a database that can be extended to connect to any data management system.

Extending WinRQA II, series of recurrence measures

Fri, 27 Jan 2017 00:00:00 GMT

WInRQA is an application dedicated to recurrence plots, a tool that is used in the analysis of recurrence of complex time series. In this article I will introduce a new tool that I have added to the program. Until now, the measures of quantification of recurrence (RQM) were obtained only from a static portion of the original series. With the new tool, we can obtain a series of measures by moving a window along the entire original series and calculating the corresponding measurements to each of these windows.

Drawing fractals with Iterated Function Systems (IFS)

Fri, 20 Jan 2017 00:00:00 GMT

The Iterated function systems (IFS) are a simple mathematical tool for constructing fractal sets through a series of contractive affine applications. This method was developed by M.F. Barnsley in 1985. In particular, it is useful to obtain a self-similar fractal based on iteratively applying the system of functions to any set, until arriving at a good approximation of the fractal set that constitutes the attractor of the system.

DataGridView with formula support

Fri, 13 Jan 2017 00:00:00 GMT

In this article I will present a custom DataGridView control that allows using formulas composed by arithmetic expressions and references to the different cells of the control. In addition to the class library with the control, I have prepared a small application to show how to use the different features it offers.

Universal object compiler using BNF rules II

Fri, 06 Jan 2017 00:00:00 GMT

BNFUP is a class library that implements an object compiler from the definition of a language using BNF rules. It also provides rule editing services. In this article I continue showing how to use the editor to compile and test your own objects using the language you have defined for that. I will also show you three examples of implementation.

Universal object compiler using BNF rules I

Thu, 05 Jan 2017 00:00:00 GMT

In this series of articles I will show a class library that implements a compiler that uses any language defined by BNF rules and that generates objects from a user-written class library, which must implement a simple interface so that the compiler can construct and initialize them from the source code.

Accessing the source code of database executable objects

Fri, 16 Dec 2016 00:00:00 GMT

All major database servers allow the creation of executable objects, such as functions or stored procedures, using some type of SQL extension language, such as PLSQL in Oracle or T-SQL in SQL Server, so that we can create applications to access and manipulate data in a more sophisticated way. In this article I will show how we can access the source code of these objects from any program using the catalog views of three of the most popular RDBMS, MySQL, Oracle and SQL Server.

How to integrate CLR code in SQL Server II

Fri, 09 Dec 2016 00:00:00 GMT

In this article I will continue with the integration of CLR objects into a SQL Server database by showing how to implement triggers and create user-defined data types. It is a simple way to extend the functionality of our database applications with all the power provided by the CLR of the .NET framework.

How to integrate CLR code in SQL Server I

Fri, 02 Dec 2016 00:00:00 GMT

In this article I will show you how you can easily extend the SQL of your SQL Server servers with functions and data types of the .NET Framework CLR (Common Language Runtime). To do this, I will implement a function with scalar return value, another function with table return value, a pair of aggregation functions and a stored procedure.

Extending WinRQA I, estimating delay and embedding dimension

Sat, 26 Nov 2016 00:00:00 GMT

WInRQA is an application dedicated to recurrence plots, a tool that is used in the analysis of recurrence of complex time series. In this article I will present the first extension of the application, which mainly consists of a series of tool windows that will help you to make estimates on what may be the most appropriate delay to try to reconstruct the phase space of the system attractor and select the correct embedding dimension.

Beyond chaos, randomness

Fri, 18 Nov 2016 00:00:00 GMT

In this article I will show how, through a very simple and totally deterministic process, we can move from a stationary system to a completely random one, going through periodic and chaotic dynamics. For this, I will generate several time series with these characteristics using the program R and several packages that can help us in the analysis of them.

WinRQA, a C# application to draw recurrence plots

Fri, 11 Nov 2016 00:00:00 GMT

A recurrence plot is a graphical tool used in the study of complex time series. Along with the plot we can also calculate a series of measures that allow us to perform a recurrence quantification analysis, or RQA. In this article I will present the WinRQA application, a tool to work with recurrence plots and RQA measures in a Windows environment.

Stepper motor controller with Arduino

Tue, 01 Nov 2016 00:00:00 GMT

A stepper motor is a kind of motor that, instead of rotating continuously in one direction, allows rotate in very small steps and stop and change direction very quickly, without problems of inertia. This makes these engines very suitable for mounting them in devices which perform movements that required high precision. In this article I will show how to build a simple controller to handle one of these motors through the Arduino board, along with a sample program written in CSharp that allows you to operate the motor from the computer where the plate is connected.

Implementing correspondence analysis in C#

Fri, 28 Oct 2016 00:00:00 GMT

The correspondence analysis is a statistical technique that allows us to study relationships between categorical data through optimal scaling and orthogonal projection in two or three dimensions of contingency tables. Its implementation is relatively simple, and in this article I will show an example using the csharp language. In addition, the sample program allows you to draw simple graphics with the resulting data.

PISA Data Analytics, Correspondece Analysis

Fri, 21 Oct 2016 00:00:00 GMT

The PISA database contains, in addition to the scores of students, a lot of demographic, socioeconomic and cultural data about them, collected through a series of questionnaires, that allow contextualize the academic results and make studies with a great number of variables. Most of these data are categorical, making the correspondence analysis a particularly appropriate tool to work with them. In this article I will show you how to easily perform this analysis using the ca package of the R program.

Complex Time Series VI, recurrence plots

Wed, 12 Oct 2016 00:00:00 GMT

To conclude this series on complex time series and their characterization using graphical tools I will show you a tool called recurrence plot, which allows to obtain some measures used in the recurrence quantification analysis, or RQA for its acronym in English. The recurrence is a characteristic property of deterministic dynamical systems, and consists of that two or more states of the system are arbitrarily close after a certain period of time.

Complex Time Series V, autocorrelation and extended dimension

Sat, 08 Oct 2016 00:00:00 GMT

In this new article in the series on time series with complex dynamics, I will show you a procedure to approximately reconstruct the information of a dynamic system with two or more variables from a single series, i.e. a set of data in a single dimension. What we will get from this unique series is a new one for each of the extra dimensions with which we intend to extend the model.

Recurrent neural networks and time series

Sun, 02 Oct 2016 00:00:00 GMT

The recurrent neural networks are a very appropriate tool for modeling time series. This is a type of network architecture that implements some kind of memory and, therefore, a sense of time. This is achieved by implementing some neurons receiving as input the output of one of the hidden layers, and injecting their output again in that layer. In this article I will show a simple way to use two neural networks of this kind, the Elman and Jordan ones, using the program R.

Complex Time Series IV, power spectrum and distribution

Sat, 24 Sep 2016 00:00:00 GMT

In this new article of the series dedicated to the graphic characterization of complex time series I will talk about two other graphical tools that can be useful, the power spectrum of the signal, which will be obtained through the Fourier transform, and the graph of the distribution of values of the series, a simple histogram with the frequency of the different values that also can provide us information about the series dynamics.

Complex Time Series III, Phase diagrams

Sat, 17 Sep 2016 00:00:00 GMT

In this new article in the series on graphic characterization of time series from dynamical systems with chaotic dynamics, I will talk about a way to represent such systems in the domain of space, independently of time, the phase diagram. With this type of diagram, you can see the attractors of the system. An attractor is a point, a curve, in general, a set of points to which converge the system equations, which gives us an idea of the typical behavior of that system.

Complex Time Series II, Web diagrams

Sat, 10 Sep 2016 00:00:00 GMT

I continue the series on graphic characterization of the complexity in time series using the helper application GraphStudy. In this article I will show how to construct a graph with which you can easily distinguish whether a particular series from an iterated function presents a chaotic dynamics, the web diagram.

Complex Time Series I, Basics

Fri, 02 Sep 2016 00:00:00 GMT

Many of the data sets with which we usually work are in the form of time series. A time series can be seen as the evolution of a dynamic system, characterized by some variables and parameters. Depending on the type of dynamic of the system, the series may be stationary, periodic, quasiperiodic, chaotic or random. In this series of articles, I will focus on the characterization of chaotic dynamics, which is presented by complex systems, by using graphical methods.

First Order Logic Tableaux

Fri, 19 Aug 2016 00:00:00 GMT

The Tableaux is a logical calculation tool that allows checking the validity of a conclusion from a series of premises. In the previous article I explained briefly the fundamentals of predicate logic Tableaux. In this article I will extend the program to the first-order logic, which has much more expressive capacity than predicate logic, although this makes also automatic calculation more difficult.

Logical calculation with Tableaux

Sun, 31 Jul 2016 00:00:00 GMT

The Tableaux is a logical calculus tool that is very useful to demonstrate a conclusion from a set of premises, find counterexamples or models of a set of logical formulas or demonstrate that a formula is a tautology, i.e., that is true in all possible cases. They can be used in artificial intelligence as the basis for implementing automated theorem proving.

Maximize or minimize a function using the Simplex method

Sat, 23 Jul 2016 00:00:00 GMT

There is a very common problem in linear programming which consists to find the values that make maximum or minimum the value of a linear function, given a number of restrictions on the values of their variables. For example, you may want to find a minimum cost or maximum production function. To do this, there is an algorithm developed in 1947 by George Dantzig, called Simplex, which allows perform such calculations in a simple and effective way.

Bidirectional motor controller with Arduino

Sat, 16 Jul 2016 00:00:00 GMT

The Arduino boards, with lots of analog and digital inputs and outputs, allow us to control electronic devices from a computer through an USB interface with a very simple programming using a language similar to C. There are lots of prefabricated modules for controlling motors, relays and all kinds of sensors, but, if you like electronics, like me, you can design and connect your own analog or digital circuits.

Printing Bar Codes

Sat, 09 Jul 2016 00:00:00 GMT

Sometimes it is necessary to print a bar code on a document or label. There are a lot of formats and encodings, in one or two dimensions, depending on the amount of information to be read by the terminal. In this article I will show three of the most common formats for one-dimensional codes and provide code in csharp to encode them.

Axis IP cameras with VAPIX protocol

Sun, 03 Jul 2016 00:00:00 GMT

Axis is a Swedish brand, one of the world leaders in the video surveillance IP cams market, which has an extensive catalog of camera models that cover virtually any need. All its products have a common access protocol via HTTP, the VAPIX protocol, based on CGI commands, which makes it especially interesting to know.

Database design tips

Sun, 26 Jun 2016 00:00:00 GMT

When you design a database, you can make a series of errors or omissions that, later, can result on many headaches, or you can shelve the use of some useful resources simply because of ignorance of them. In this article I will give you a few tips that can help you to better design and management of your data and applications that manage them, especially if you are a beginner.

How to copy from a DataGridView to Excel

Sat, 25 Jun 2016 00:00:00 GMT

When multiple rows are selected in a DataGridView control and Ctrl+C is pressed to copy its content, the default behavior copies the cell values in plain text format separated by tabulators. Just with this you can paste the data into an Excel spreadsheet, but you can implement this behavior in a more sophisticated way, applying a custom format to the columns depending on the data type of each cell.

How to build an expressions analyzer, implementation II

Sat, 18 Jun 2016 00:00:00 GMT

In the previous article in this series I began to show how to implement an arithmetic expression analyzer, or parser, from the grammar rules in BNF notation, with classes which extract numbers, variables and constants. In this article I will finish the series with the implementation of the class focused in working with the main rule, which analyzes the expressions themselves. I will also provide a small sample application that draws the graph corresponding to the expression from the object generated by the compiler.

How to build an expressions analyzer, implementation I

Fri, 17 Jun 2016 00:00:00 GMT

In the previous article in this series I reviewed the main issues about the design of the grammar to build an analyzer, or parser, for arithmetic expressions. In this article I will show the first part of its implementation from the BNF grammar rules, converting the input expression, in the form of a text string, in a series of objects that we can use to evaluate it and give different values to the constants and variables that compose it.

How to build an expressions analyzer, grammar

Tue, 14 Jun 2016 00:00:00 GMT

When we are working with mathematical functions, it is very convenient to have a parser that allows us to write and perform different versions of the equations that must be processed by the program, rather than having to modify and recompile the code to adapt it to these changes each time. In this series of articles I will show how to build a simple but powerful expressions analyzer, which can be extended easily to deal with more sophisticated expressions, starting by explaining in this article the basic theory necessary to successfully face this kind of development.

The PropertyGrid Control, Type converters

Fri, 10 Jun 2016 00:00:00 GMT

To conclude this series on the PropertyGrid control I will show you how to use different type converters derived from the TypeConverter class to customize how they are displayed or edited the properties. The .NET framework provides converters for many types of properties, but you can also easily implement your own converters by deriving a class from TypeConverter or a specialized converter and overloading a few functions.

The PropertyGrid Control, events and custom editors

Sat, 04 Jun 2016 00:00:00 GMT

In the previous article in this series I did show how to use the basic features of the PropertyGrid control to edit the properties of a particular object or collection of objects. In this article I will show you the most important events of this control as well as the implementation of custom editors that allow editing of properties of types for which there is no default editor, such as the classes developed by yourself in your program.

The PropertyGrid Control, basics

Sat, 28 May 2016 00:00:00 GMT

One of the GUI (graphic user interface) controls more versatile that the .NET framework offers is the PropertyGrid. It is a component through which the user can edit all the properties of an object that the developer has configured, allowing structuring them into categories and sort them alphabetically. It also provides many options to customize both presentation and editing of their properties and shows the user a help text on each one of them. In this series I will show a complete tutorial on using this control and its main features, starting with this article on its basic use.

IP Camera NetWave CGI protocol

Sat, 14 May 2016 00:00:00 GMT

Many of the network IP cameras that can be found on the market use the Netwave protocol, based on CGI commands to obtain video images through an internal http server. In this article I will show how to build a simple application to control these cameras, which are typically used for surveillance and can make scan motions in addition to providing video images.

A basic video capture application using DirectShow

Thu, 05 May 2016 00:00:00 GMT

In the previous article in this series, I did a summary of the basic components of DirectShow: filters, filter graphs and pins to connect the elements together, and how we can identify them using the GraphEdit tool of the SDK. In this article I will show how to build a "simple" application to capture and playback video using the interfaces provided in DirectShow, a subset of the COM distributed object model from Microsoft.

Basic concepts in DirectShow programming

Sat, 30 Apr 2016 00:00:00 GMT

Currently there are a lot of video capture devices commercially available; anyone can buy a digital camera or a webcam at a reasonable price. All of these devices can be easily controlled from a program developed by ourselves using Microsoft DirectShow. DirectShow is a set of interfaces that provide a generic API with which you can capture and play audio and video regardless of the brand or model of camera you are using. It also allows recording and playback of files in any format.

Random numbers generation

Sun, 24 Apr 2016 00:00:00 GMT

In many applications it is necessary to generate random numbers. To do so, the .NET framework provides the Random class, which can generate uniformly distributed pseudo-random values, which means that all numbers are equally likely to appear in the result. But in some cases we need to generate random values that follow other different types of distribution. In this article we will see how to generate random numbers that follow a normal distribution, with a system that can be extended to any other type of distribution.

What is a complex system?

Sat, 09 Apr 2016 00:00:00 GMT

Usually, when you perform a data analysis, you suppose that they come from a normal distribution. In fact, you perform a battery of tests to verify that this assumption is met and, otherwise, you try to modify the data so that it is satisfied. This is because most analysis techniques only work properly on normally distributed data. But there are a number of systems that present a complex dynamics where is not valid to apply this hypothesis and wherein adjusting the data only leads to distortions that invalidate the results.

DbTextFinder Application for search text in databases

Sat, 02 Apr 2016 00:00:00 GMT

The catalog views contain all the information concerning the structure of the database: schemas, tables, table fields, data types of the fields, integrity constraints, stored procedures code, etc. The knowing of them is essential to develop tools for data management independent of the structure. In this article we will view an example of one of these tools, DBTextFinder, a simple application that will allow us to search for text in the records of our database and within the code of the views and stored procedures.

PISA Data Analytics, the Student Scores

Sat, 12 Mar 2016 00:00:00 GMT

In the previous article in this series we viewed how to computing standard errors with replicate weights in PISA database, in this article we will take an overview of one of the most controversial points of these studies, the complex system of scores implemented.

PISA Data Analytics, Sample Weights and Replicate Weights

Sun, 28 Feb 2016 00:00:00 GMT

In the previous article in this series we saw an introduction to PISA data analytics, with examples of functions in R code for sampling, and we talked about the sampling weights, which ponder each student so that it represents a group of individuals with the same characteristics rather than a single student, (remember that PISA aims to assess the effect of educational policies on the whole population of the country, not on individual students). In this article, we will see how to use these weights to calculate estimators from samples and we'll see also how to calculate standard errors of these estimators using replicated weights.

Introduction to PISA Data Analytics

Fri, 19 Feb 2016 00:00:00 GMT

Every three years, since 2000, the OECD (Organization for Economic Cooperation and Development) performs a series of tests in a number of countries at national level to 15-years-old students, in order to assess the degree of knowledge in three main groups of areas: science, reading and math. This is the PISA program, whose last edition took place in 2015.

Using WinPODUtil to process CSV files

Fri, 12 Feb 2016 00:00:00 GMT

In the previous article we saw how to query POD databases with the WinPODUtil program, in this article we will see how to use the tool to process the CSV files generated by the queries, or any other CSV file. The format of these files consists in a series of text lines, the first of which must contain the column headings, separated by the semicolon character (;). Each line, except the first, represents one data record.

WinPODUtil Application to Query POD Databases

Fri, 05 Feb 2016 00:00:00 GMT

In previous articles I have talked about the POD project, a database that centralizes access to other databases so that they can be consulted through a common interface. In this article we will see the tool that is used for data filtering and query on any of the databases integrated into POD.

Introduction to PISA Database

Sat, 30 Jan 2016 00:00:00 GMT

PISA (Program for International Student Assessment) is a program of the OECD (Organization for Economic Cooperation and Development) for the evaluation of education policies. It consists of a series of tests and surveys conducted to 15 years old students, schools and parents at national level in the countries participating in the program (in 2012 there were 65 participating countries, and in 2015 there are more than 70). These tests seek to assess the level of knowledge in three main areas: Reading, science and math.

In this article I make a brief introduction to SQL Server database created from the original data published by the OECD.

POD Configuration Database

Thu, 07 Jan 2016 00:00:00 GMT

POD (Portal Open Data) is a project that I started when I was studying to obtain Microsoft Web Developer MCSD, in order to do some practices. Consists of a SQL Server database through which on can access to other databases in a centralized way.

In this article I describe the POD Configuration database

How to remove spam traffic in Google Analytics

Sat, 02 Jan 2016 00:00:00 GMT

All users of Google Analytics end up suffering the attacks of a legion of referral spam bots that distorting all data obtained from your website, this traffic can come to represent an amount much higher than the actual traffic visits.

In this article I explain how to remove all traffic of this type definitively from our statistics.