Running Variance

Just in mid of the code wanted to find the Running Variance, just as habit typed and found not so good links.

1/N*[sum(i=1:N-1, Xi*Xi') + X*X'] – (1/N^2)*[ sum(i=1:(N-1), Xi) + X][ sum(i=1:(N-1), Xi) + X]‘

Matlab code for calculating the running Variance is as follow

%updating Mean

newMean = (newMean*(N-1) + X)/N;

sumOfSq = sumOfSq*(N-1)  + X*X';

covMat =  (1/N)*sumOfSQ - newMean*newMean'

Externally there are few links that are worth reading

• Accurately computing running variance
• From Google Answers, someone gave even the posted Java Code ; Simple and clear that could be easily read by any one knowing any programming language

Using Many Colors in the Matlab

While using the ‘plot’ function you end up using only small number of colors. I searched online to see if there are any solutions

One is given by http://blogs.mathworks.com/pick/2008/08/15/colors-for-your-multi-line-plots/

It discusses “varycolor” file. Which is very nice for generating many colors on the run.

However I found that for plotting of the poitns and data following is much distinguishable.

It is 72 element array.

clr = [ '.r';'.b'; '.g'; '.c';'.m'; '.y';...
        '*r';'*b'; '*g'; '*c';'*m'; '*y';...
        'xr';'xb'; 'xg'; 'xc';'xm'; 'xy';...
        '+r';'+b'; '+g'; '+c';'+m'; '+y';...
        'or';'ob'; 'og'; 'oc';'om'; 'oy';...
        'dr';'db'; 'dg'; 'dc';'dm'; 'dy';...
        'sr';'sb'; 'sg'; 'sc';'sm'; 'sy';...
        'pr';'pb'; 'pg'; 'pc';'pm'; 'py';...
        'hr';'hb'; 'hg'; 'hc';'hm'; 'hy';...
        'vr';'vb'; 'vg'; 'vc';'vm'; 'vy';...
        '>r';'>b'; '>g'; '>c';'>m'; '>y';...
        '.k';'xk'; '*k'; '+k';'ok'; 'dk';...
        ];

stl Sort in C++; simple code for sorting the array of structures

Simple Code that shows how to use the C++ STL function sort()

<blockquote>
#include <iostream>
#include <algorithm>

using namespace std;

struct Numb{
double num;
int pos1;

bool operator &lt;(const Numb &amp;n1){
return num &lt; n1.num;
};
};
////////////////////////////////
void main(void){

Numb numb[10];

for(int i=0; i &lt; 10; i++){
numb[i].num = rand();
numb[i].pos1 = i;
}
cout &lt;&lt; endl &lt;&lt; "---------" &lt;&lt;endl;
for(int i=0; i &lt; 10; i++){
cout &lt;&lt; " " &lt;&lt; "(" &lt;&lt; numb[i].pos1 &lt;&lt; ") " &lt;&lt; numb[i].num;
}
cout &lt;&lt; endl &lt;&lt; "---------" &lt;&lt;endl;

std::sort( numb, numb+10);
cout &lt;&lt; endl &lt;&lt; "---------" &lt;&lt;endl;
for(int i=0; i &lt; 10; i++){
cout &lt;&lt; " " &lt;&lt; "(" &lt;&lt; numb[i].pos1 &lt;&lt; ") " &lt;&lt; numb[i].num;
}

cout &lt;&lt; endl &lt;&lt; "---------" &lt;&lt;endl;

}

OpenCv; Small Code using Erode and Dilate

Small Code that reads pbm image, convert it into 1 channel image. Erodes it, dilates it and shows them

#include <float.h>

#include <limits.h>

#include <time.h>

#include <ctype.h>

#include <iostream>

#include "BlobResult.h"

#include "blob.h"

#ifdef _EiC

#define WIN32

#endif

using namespace std;

void main(void){

IplImage *inputImage = cvLoadImage( "0584.pbm", 1 );

IplImage *gray = cvCreateImage( cvSize(inputImage->width,inputImage->height), 8, 1 );

cvCvtColor( inputImage, gray, CV_BGR2GRAY );

IplImage*img = inputImage;

inputImage = gray;

::cvReleaseImage(&img);

cvNamedWindow( "orig", 1 );

cvShowImage( "orig", inputImage );

IplImage *outputImage;

IplImage *outputImage2;

outputImage = cvCreateImage( cvSize( inputImage->width, inputImage->height ), IPL_DEPTH_8U, 1 );

outputImage2 = cvCreateImage( cvSize( inputImage->width, inputImage->height ), IPL_DEPTH_8U, 1 );

cvErode(inputImage, outputImage, 0, 1);

cvNamedWindow( "erode", 1 );

cvShowImage( "erode", outputImage );

 

cvDilate(outputImage, outputImage2, 0, 2);

cvNamedWindow( "dilate", 1 );

cvShowImage( "dilate", outputImage2 );

cvReleaseImage(&outputImage);

cvReleaseImage(&outputImage2);

cvWaitKey();

 

return;

}>