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/*=================================================================
* COMPUTE_ERRORS computes classification error and area under ROC.
*
* Synopsis:
* [error,auc] = compute_errors(score,true_labels)
*
* Input:
* scores [1 x n] scores of binary classifier; the classifier decides
* according to the sign of the score.
* true_labels [1 x n] true labels; 1st class label = 1,
* 2nd class label != 1
* Output:
* error [1x1] number of mis-classifications
* auc [1x1] Area under ROC
*
*=================================================================*/
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <mex.h>
#include <sys/time.h>
#include <time.h>
#include <errno.h>
#include "libocas.h"
#include "ocas_helper.h"
#if !defined(MX_API_VER) || MX_API_VER<0x07040000
#define mwSize int
#define mwIndex int
#endif
/*======================================================================
Main code.
========================================================================*/
void mexFunction( int nlhs, mxArray *plhs[],int nrhs, const mxArray *prhs[] )
{
int *true_labels_int;
uint32_t n1, n2, i;
double auc, error;
double *scores, *true_labels;
if( nrhs != 2 )
mexErrMsgTxt("Two input arguments must be passed.\n"
"\n"
"[error,auc] = compute_errors(score,true_labels)\n"
"Inputs: score [N x 1 (double)] positive class score >= 0 otherwise negative class \n"
" true_labels [N x 1 (double)] positive class 1; negative class ~= 1\n"
"Outputs: error [1x1] number of misclassifications\n"
" auc [1x1] Arrea Under ROC\n");
scores = mxGetPr(prhs[0]);
true_labels = mxGetPr(prhs[1]);
n1 = LIBOCAS_MAX(mxGetM(prhs[0]),mxGetN(prhs[0]));
n2 = LIBOCAS_MAX(mxGetM(prhs[1]),mxGetN(prhs[1]));
if(n1 != n2)
mexErrMsgTxt("The input vectors must be of the same size.");
true_labels_int = mxCalloc(n1,sizeof(int));
if(true_labels_int == NULL)
mexErrMsgTxt("Not enough memory.");
error = 0;
for(i = 0; i < n1; i++)
{
true_labels_int[i] = (int)true_labels[i];
if((true_labels[i] == 1 && scores[i] <= 0) || (true_labels[i] != 1 && scores[i] > 0))
error++;
}
auc = compute_auc(scores, true_labels_int, n1);
mxFree(true_labels_int);
plhs[0] = mxCreateDoubleScalar(error);
plhs[1] = mxCreateDoubleScalar(auc);
return;
}
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