sushil bajracharya's blog

getting tab separated values from postgres query

2009-11-04T10:50:00.001-08:00

I keep forgetting this..

TUPLE MODE              #\t
DISABLE FIELD ALIGNMENT #\a
TAB AS DELIMITER        #\f '\t'
O/P TO FILE             #\o ~/out.txt
RUN QUERY               #select …

Inverting colors in PDF

2009-10-30T18:30:00.000-07:00

I am surprised that there does not seem to be an easy way to invert the colors in a PDF documents. Preview in mac allows to apply Quartz filters while doing a 'save as', but why inverting colors is not listed as one of the options? Adobe's reader allows you to substitute colors in Preferences but it does not work in a PDF that someone had tried to make prettier by putting strong colors as background.

The solution that worked for me was using mogrify. It uses ImageMagik for doing the magic. Basically you can execute something like this in the Terminal:

$ mogrify -negate badly-colored.pdf

But this did not fully solve the problem, I got a PDF whose background - out of the page's margin - was all black. The result looked as each page had thick black borders. Thanks to Preview this time, I was able to crop those margins out. First, make a rectangular selection, then select all PDFs in the thumbnail view, then apply crop. The end result was something workable.

melting and casting tables

2009-10-12T14:16:00.000-07:00

Hours after searching for how to do this in R, I finally found the right solution. The problem is, you have a table of counts like this

Item, Red, Blue, Green
----------------------------
Apple, 2, 3, 1
Ball, 0, 0, 3

I wanted to convert it to a table as follows

Item, Color, Count
------------------------
Apple, Red, 2
Apple, Blue, 3
Apple, Green, 1
Ball, Red, 0
Ball, Blue, 0
Ball, Green, 3

I had a hard time expressing this as a problem statement. What do I search for? I tried something like "converting variables to single column", "reversing contegency table" blah blah.. At the end, not sure with what query, I ended up here. How on earth should I know that a function called 'melt' could do what I want. So much for being metaphorical.

patch/build/test field collapsing with solr

2009-09-02T15:52:00.000-07:00

This entry shows everything you need to path and build solr 1.3 with the field collapsing feature. To use the latest patch, do this:

wget --no-check-certificate https://issues.apache.org/jira/secure/attachment/12417524/field-collapse-5.patch

svn co http://svn.apache.org/repos/asf/lucene/solr/trunk/ ./apache-solr-trunk/

cd apache-solr-trunk/

 

patch -p0 <../field-collapse-5.patch 

ant example

Update: It seems the above patch on the trunk has no effect of field collapsing but the patch as suggested in the link with 1.3 works. Also don't forget to register the collapse component for all handlers you with to use, eg: standard and dismax.