www.pudn.com > colorseg.zip > hist5hel.c, change:2003-03-03,size:1467b

/* A replacement for fast(sparse(S,1,1,n,1)) because this should be fast. 
 * 
 * Usage x=hist5hel(S,n) with all elements of S integers in the 
 * range 1..n gives x(i)=sum(S==i). 
 *  
 * Written for Matlab 5 by Hans Olsson 1997-06-26 
 *    Department of Computer Science 
 *    Lund University 
 *    Sweden 
 * 
 *    E-mail: Hans.Olsson@dna.lth.se 
 * 
 *           
 */ 
 
 
#include <math.h> 
#include <ctype.h> 
#include "mex.h"  
          /* mex.h is included with the Matlab shipment */ 
 
 
/* some preprocessor definitions */ 
 
#define	min(A, B)	((A)  (B) ? (A) : (B)) 
#define mrows(A)	(mxGetM(A)) 
#define ncols(A)	(mxGetN(A)) 
#define realdata(A)	(mxGetPr(A)) 
 
void mexFunction(int nlhs,mxArray*plhs[],int nrhs,const mxArray*prhs[])  
{ 
  const double *y_in; 
  long int n,i,n_in; 
  double *x_out; 
  if (nrhs<1 || nrhs>2)  
    mexErrMsgTxt("histmultihelp.c: wrong number of input arguments."); 
  if (nlhs !=1 )  
    mexErrMsgTxt("histmultihelp.c: wrong number of output arguments."); 
 
  y_in=realdata(prhs[0]); 
  n=*realdata(prhs[1]); /* Range of data is 1..n */ 
 
  plhs[0]=mxCreateDoubleMatrix(n,1,mxREAL); 
  x_out=realdata(plhs[0]); 
 
  n_in=mxGetM(prhs[0])*mxGetN(prhs[0]); 
 
  /* Zero all elements :*/ 
  for(i=0;i<n;i++) x_out[i]=0.0; 
 
  /* Go through the elements and add the to their positions */ 
  for(i=0;i<n_in;i++) { 
    long int index=y_in[i]; 
    if ((index>=1)&&(index=n)) 
      x_out[index-1]+=1.0; 
  }; 
}