MATLAB Central Newsreader Recent Posts

Logistic regression

Amit — Wed, 19 Jun 2013 21:16:09 +0000

I am looking to find something analogous to stepwise linear regression for logistic regression. I have 12 independent variables and I want to test them each one by one to understand if the model improves.

I am using mnrfit right now and it does not provide the adjusted R square value as well. Is there any way I could get that stats in mnrfit too.

Thanks very much in advance.

Amit Siroya

Can not pass variable to ode45

Sandip — Wed, 19 Jun 2013 21:12:10 +0000

Hi:
Please suggest a way... I have a command as below to solve the ode by ode45 and I need to pass three variables.
[x,y]=ode45(@fnode,xspan,y0,c1,c2,c3);

I have defined the function in .m file as
function yprime = fnode(x,y,c1,c2,c3)

However, I can not read in the c3 in the function (ode) file. c1 & c2 are coming alright.

Please help.

ginput modifications --- How?

Virgil Stokes — Wed, 19 Jun 2013 21:06:10 +0000

My problem is based on ginput which returns the (x,y) coordinates of a large cross-hair when the left-button mouse is clicked. The modified ginput would use a vertical line as a pointer (not a crosshair), and it would return the x-coordinate of the position of the vertical line when the left mouse-button is clicked. How can I modify ginput to accomplish this?

Beep function doesn't work

Chenchen — Wed, 19 Jun 2013 20:40:14 +0000

I would like to use beep function in my m file. The code is
beep on
beep
But no beep sound was produced. I've checked the setting of Windows default sound. It has been set enabled. Anyone can help me out? Help much appreciated!!

Re: Error : Inner matrix dimensions must agree When computing the three dimensional integral.

yolanda — Wed, 19 Jun 2013 20:39:07 +0000

Hi, thanks for your reply. But I don't think something wrong with the matrix dimensions.
The first matrix is 1*3, the second one is 3*3, and the last one is 3*1.
So it should give the result of 1*1 matrix...

Any comments?

Thanks

"someone" wrote in message <kpt46r$qf3$1@newscl01ah.mathworks.com>...
> "yolanda" wrote in message <kpskm1$d1b$1@newscl01ah.mathworks.com>...
> > Error : Inner matrix dimensions must agree When computing the three dimensional integral.
>
> I don't have MATLAB installed on this computer,
> but I'm wondering if you have the commas & semicolons
> reversed in your anonymous function handle statement.
>
> Just a thuoght since no one else has replied.

Re: Error : Inner matrix dimensions must agree When computing the three dimensional integral.

yolanda — Wed, 19 Jun 2013 20:35:09 +0000

HI, thanks for your reply. But I think the matrix dimensions are matched.
The first one is 1*3 matrix, the second is 3*3, the last one is 3*1.
So it should come out the result of 1*1 matrix.

Any comments ?

Thanks

"someone" wrote in message <kpt46r$qf3$1@newscl01ah.mathworks.com>...
> "yolanda" wrote in message <kpskm1$d1b$1@newscl01ah.mathworks.com>...
> > Error : Inner matrix dimensions must agree When computing the three dimensional integral.
>
> I don't have MATLAB installed on this computer,
> but I'm wondering if you have the commas & semicolons
> reversed in your anonymous function handle statement.
>
> Just a thuoght since no one else has replied.

Re: Error : Inner matrix dimensions must agree When computing the three dimensional integral.

someone — Wed, 19 Jun 2013 20:27:07 +0000

"yolanda" wrote in message <kpskm1$d1b$1@newscl01ah.mathworks.com>...
> Error : Inner matrix dimensions must agree When computing the three dimensional integral.
>
> The code is as follows:
>
> m1 = 20;
> v1 = 60;
> m2 = 20;
> v2 = 60;
> m3 = 20;
> v3 = 60;
> cov = [ 60,0,0;
> 0,60,0;
> 0,0,60]
> cov1=inv(cov)
>
> f = @(z,y,x) exp( ([(x-m1),(y-m2),(z-m3)]*(cov1)*[(x-m1);(y-m2);(z-m3)])./(-2) )
> P1 = triplequad(f,0,1000,0,1000,0,1000);
>
> I am eager to getting the solution.... Anyone has any comments? I would appreciate !!!!!

I don't have MATLAB installed on this computer,
but I'm wondering if you have the commas & semicolons
reversed in your anonymous function handle statement.

Just a thuoght since no one else has replied.

Re: GreyScale Image Analysis

Matt — Wed, 19 Jun 2013 20:22:08 +0000

I want to add my attempt so far, but im having some errors.

Attempt:
%Find the location of the max brightness on the line segment (0 is black, 255 is white)
    maxValue = 0;
    for m = 1:((xmax-xmin)+1)
        if ((hsc_image(y,(xmin + m - 1)))> maxValue)
             maxValue = (hsc_image(y,(xmin + m - 1))) ;
        end
    [row col] = find((hsc_image(y,xmin:xmax)) == maxValue);
    end
plot(frames_time,row);

Errors:

Error using plot
Vectors must be the same lengths.

Error in Matthew_Morelli_Lightning_Video_Processing (line
101)
plot(frames_time,row);

Error in run (line 64)
evalin('caller', [script ';']);

Re: read numerical text file by fixed column width, no delimiters

dpb — Wed, 19 Jun 2013 20:06:42 +0000

On 6/19/2013 2:36 PM, Kristin wrote:
...

OK, here's a very rough, not terribly user=friendly outline, but should
get the job done...

program tentoeleven
   character(len=132):: fold, fnew ! A filename for old, new file
   real :: v(8) ! Data array of 8 floats

   read(*,*) fold ! It'll wait for you...
   open(11,file=fold,action='read',status='old')

   read(*,*) fnew ! It'll wait for you...
   open(12,file=fnew,action='write',status='new')

   ios=0
   do while(ios.eq.0)
     read(11,'(F10.4)',iostat=ios) v ! read the old file F10.4
     write(12,'(F11.4)') v ! F11.4 will insert space delimiter
   end do

   close(11)
   close(12)
end

Will continue 'til EOF condition on the old file at which time the
IOSTATUS variable will become <0. Of course, other errors will also
abort, but one presumes the files are otherwise, clean.

--

Re: Build up a given matrix from a set of matrices

james bejon — Wed, 19 Jun 2013 19:38:07 +0000

P.S. Could you post your algorithm that works for smaller sizes, just so I can make sure I've understood the problem correctly?

Re: read numerical text file by fixed column width, no delimiters

Kristin — Wed, 19 Jun 2013 19:36:11 +0000

dpb <none@non.net> wrote in message <kpq7fb$i95$1@speranza.aioe.org>...
> On 6/17/2013 6:15 PM, Kristin wrote:
> > I have a large text file containing 8 columns of numbers and each column
> > has a fixed width of 10 characters (so the total length of each row is
> > 80 characters). The first character in each group of 10 characters is
> > either a space or a negative sign.
> > So for example a typical line is:
> > -1.6999E-3-1.3266E-3 1.2916E-3 3.5491E-4 1.1022E-3-9.5555E-4-3.9528E-4
> > 3.5200E-4
> > I was trying various approaches with textread or textscan and was trying
> > to use %c because %s requires whitespace separated values which is not
> > always the case here. Is there an easy way to read such a file in
> > Matlab? I either need eight vectors of numbers (ideally)...
>
> Oh, forgot another "trick" I've used on occasion. How well it works
> depends on the size of the file...if can hold in memory works pretty
> good; if have to can do in "chunks" that do fit...
>
> Given you have a line as yours above I make it two to demonstrate for
> the general case...
>
> >> m=[l;l];
> >> v=reshape(str2num(reshape(m',10,[])'),8,[])'
> v =
> -0.0017 -0.0013 0.0013 0.0004 0.0011 -0.0010 -0.0004 0.0004
> -0.0017 -0.0013 0.0013 0.0004 0.0011 -0.0010 -0.0004 0.0004
> >>
>
> Just have to know the number per line and the width of the field for the
> two reshape() operations. The first casts the input character array
> into a column of the right number of characters/line one field/row; the
> second recasts into the known number of entries/line.
>
> Again and still a lot of machinations for what _should_ be doable
> directly by the i/o runtime formatting but C is "just broke" in this regard.
>
> --

Thanks for the suggestions. I will try one of those methods (reshape or fgetl to do it a line at a time). Otherwise I'll see if I can just make a quick fortran script although I haven't previously used fortran for my coding.

Kristin

Re: Fractional order trasfer function in matlab

LUIS munoz — Wed, 19 Jun 2013 19:08:13 +0000

"Venu" wrote in message <hgcjm7$s02$1@fred.mathworks.com>...
> The folder in which the file fotf is present must be named as @fotf

I am now runnig this piece of matlab software:

kp=2.872185234368413;
ki=5.729820976261658;
niu=0.5784;

reg= fotf([1,0],[niu,0],[kp, kp*ki],[niu,0]);
H=fotf([1.7,1],[1,0],[1],[0]);
figure(1),bode(H*reg)

The error is:

??? Access to an object's fields is only permitted within its methods.

Error in ==> mtimes at 3
a=kron(G1.a,G2.a);

Could you please help me with this?. Thanks a lot. Luis

Re: Build up a given matrix from a set of matrices

james bejon — Wed, 19 Jun 2013 19:08:13 +0000

Well, this is nothing to do with your algorithm as such. But the first thing that occurs to me is that you could easily convert each row into a single number; suppose, for instance, your integers are both int8; you could then make that a single int16, e.g.,

n1 = [int8(10), int8(20)];

t = typecast(n1, 'int16');

n2 = typecast(t, 'int8');

isequal(n1, n2)

You could then reduce your problem to dealing with single numbers rather than rows all the time, which might make life easier and quicker.

Meanwhile, I'll have a think about the algorithm itself and let you know if anything springs to mind...

Running fotf

LUIS munoz — Wed, 19 Jun 2013 19:02:10 +0000

Hello nice helpers, I am trying to run this piece of software:

kp=2.872185234368413;
ki=5.729820976261658;
niu=0.5784;

reg= fotf([1,0],[niu,0],[kp, kp*ki],[niu,0]);
H=fotf([1.7,1],[1,0],[1],[0]);
figure(1),bode(H*reg)

But here I got the error:

??? Access to an object's fields is only permitted within its methods.

Error in ==> mtimes at 3
a=kron(G1.a,G2.a);

Could you please help me with this error?. Thanks a lot. Luis

Re: How to use Split function in Matlab.

dpb — Wed, 19 Jun 2013 17:41:12 +0000

On 6/19/2013 8:54 AM, dpb wrote:
> On 6/19/2013 7:20 AM, dpb wrote:
...

> OK, here's the utility I threw together and keep around for such simple
> parsing...no error handling and nothing but simple-minded included. :)
>
> I couldn't recall what I had name it earlier...obviously by that it's
> not used much, but is handy on occasion.
>
> function tok = tokens(s,d)
> % Simple string parser returns tokens in input string s
> %
> % STRTOK(S) the tokens in the string S delimited
> % by "white space". Any leading white space characters are ignored.
> %
> % STRTOK(S,D) returns tokens delimited by one of the
> % characters in D. Any leading delimiter characters are ignored.
>
> % Rev: 1.0 DPBozarth 5Jun2000
>
...

And I just noticed for the first time I never fixed the help text to
match the function name...clear it doesn't get much attention. :)

function tok = tokens(s,d)
% Simple string parser returns tokens in input string s
%
% TOKENS(S) the tokens in the string S delimited
% by "white space". Any leading white space characters are ignored.
%
% TOKENS(S,D) returns tokens delimited by one of the
% characters in D. Any leading delimiter characters are ignored.

--