kmatrix.c

很好用的统计模式识别工具箱

/* --------------------------------------------------------------------
 [K] = kmatrix( data, ker, arg )
 Computes kernel matrix.

 Make executable file by a command 'mex kmatrix.c kernel.c'.

  mandatory inputs:
   data [D x N ] matrix of N training D-dimensional patterns.
   ker [string] kernel identifier: 'linear', 'poly', 'rbf'.
   arg [real] kernel argument.

  mandatory outputs:
   K [D x D] kernel matrix.


 Statistical Pattern Recognition Toolbox, Vojtech Franc, Vaclav Hlavac
 (c) Czech Technical University Prague, http://cmp.felk.cvut.cz
 Written Vojtech Franc (diploma thesis) 02.11.1999

 Modifications:
 21-October-2001, V.Franc.
 30-September-2001, V.Franc, created.
 -------------------------------------------------------------------- */

#include "mex.h"
#include "matrix.h"
#include <math.h>
#include <stdlib.h>
#include <string.h>

#include "kernel.h"

/* case insensitive string comparision */
#ifdef __BORLANDC__
   #define STR_COMPARE(A,B,C)      strncmpi(A,B,C)  /* Borland */
#else
  #define STR_COMPARE(A,B,C)      strncasecmp(A,B,C) /* Linux gcc */
#endif

/* ==============================================================
 Main MEX function - interface to Matlab.
============================================================== */
void mexFunction( int nlhs, mxArray *plhs[],
		  int nrhs, const mxArray*prhs[] )
{
   long i, j, N;
   double tmp;
   double *K;
   char skernel[10];

   /* ---- check number of input arguments  ------------- */

   if(nrhs < 3)
      mexErrMsgTxt("Not enough input arguments.");
   if(nlhs < 1)
      mexErrMsgTxt("Not enough output arguments.");


   /* ---- check input arguments  ----------------------- */

   /* data matrix [dim x N ] */
   if( !mxIsNumeric(prhs[0]) || !mxIsDouble(prhs[0]) ||
       mxIsEmpty(prhs[0])    || mxIsComplex(prhs[0]) )
      mexErrMsgTxt("Input X must be a real matrix.");

   /* a string as kernel identifier ('linear',poly','rbf' ) */
   if( mxIsChar(prhs[1]) != 1 || mxGetM(prhs[1]) != 1 )
      mexErrMsgTxt("Input ker must be a string");
   else {
       /* check which kernel  */
       mxGetString( prhs[1], skernel, 10 );
       if( STR_COMPARE( skernel, "linear", 6) == 0 ) {
          ker = 0;
       } else if( STR_COMPARE( skernel, "poly", 4) == 0 ) {
          ker = 1;
       } else if( STR_COMPARE( skernel, "rbf", 3) == 0 ) {
          ker = 2;
       } else
          mexErrMsgTxt("Unknown kernel identifier.");
   }

   /*  real input argument for polynomial and rbf kernel   */
   if( ker == 1 || ker == 2) {
      if( !mxIsNumeric(prhs[2]) || !mxIsDouble(prhs[2]) ||
         mxIsEmpty(prhs[2])    || mxIsComplex(prhs[2]) ||
         mxGetN(prhs[2]) != 1  || mxGetM(prhs[2]) != 1 )
         mexErrMsgTxt("Input arg must be a real scalar.");
      else {
         arg1 = mxGetScalar(prhs[2]);  /* take kernel argument */

         /* if kernel is RBF than recompute its argument */
         if( ker == 2) arg1 = -2*arg1*arg1;
      }
   }

   /* ---- init variables ------------------------------- */

   dataA = mxGetPr(prhs[0]);    /* pointer at patterns */
   dataB = dataA;
   dim = mxGetM(prhs[0]);       /* data dimension */
   N = mxGetN(prhs[0]);         /* number of data */

   /* creates output kernel matrix. */
   plhs[0] = mxCreateDoubleMatrix(N,N,mxREAL);
   K = mxGetPr(plhs[0]);

   /* computes kenrel matrix. */
   for( i = 0; i < N; i++ ) {
      for( j = i; j < N; j++ ) {
         tmp = kernel( i, j );
         K[i*N+j] = tmp;
         K[j*N+i] = tmp;
      }
   }
}