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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "mex.h"
#ifdef MX_API_VER
#if MX_API_VER < 0x07030000
typedef int mwIndex;
#endif
#endif
void exit_with_help()
{
mexPrintf(
"Usage: libsvmwrite('filename', label_vector, instance_matrix);\n"
);
}
static void fake_answer(int nlhs, mxArray *plhs[])
{
int i;
for(i=0;i<nlhs;i++)
plhs[i] = mxCreateDoubleMatrix(0, 0, mxREAL);
}
void libsvmwrite(const char *filename, const mxArray *label_vec, const mxArray *instance_mat)
{
FILE *fp = fopen(filename,"w");
mwIndex *ir, *jc, k, low, high;
size_t i, l, label_vector_row_num;
double *samples, *labels;
mxArray *instance_mat_col; // instance sparse matrix in column format
if(fp ==NULL)
{
mexPrintf("can't open output file %s\n",filename);
return;
}
// transpose instance matrix
{
mxArray *prhs[1], *plhs[1];
prhs[0] = mxDuplicateArray(instance_mat);
if(mexCallMATLAB(1, plhs, 1, prhs, "transpose"))
{
mexPrintf("Error: cannot transpose instance matrix\n");
return;
}
instance_mat_col = plhs[0];
mxDestroyArray(prhs[0]);
}
// the number of instance
l = mxGetN(instance_mat_col);
label_vector_row_num = mxGetM(label_vec);
if(label_vector_row_num!=l)
{
mexPrintf("Length of label vector does not match # of instances.\n");
return;
}
// each column is one instance
labels = mxGetPr(label_vec);
samples = mxGetPr(instance_mat_col);
ir = mxGetIr(instance_mat_col);
jc = mxGetJc(instance_mat_col);
for(i=0;i<l;i++)
{
fprintf(fp,"%g", labels[i]);
low = jc[i], high = jc[i+1];
for(k=low;k<high;k++)
fprintf(fp," %lu:%g", (size_t)ir[k]+1, samples[k]);
fprintf(fp,"\n");
}
fclose(fp);
return;
}
void mexFunction( int nlhs, mxArray *plhs[],
int nrhs, const mxArray *prhs[] )
{
if(nlhs > 0)
{
exit_with_help();
fake_answer(nlhs, plhs);
return;
}
// Transform the input Matrix to libsvm format
if(nrhs == 3)
{
char filename[256];
if(!mxIsDouble(prhs[1]) || !mxIsDouble(prhs[2]))
{
mexPrintf("Error: label vector and instance matrix must be double\n");
return;
}
mxGetString(prhs[0], filename, mxGetN(prhs[0])+1);
if(mxIsSparse(prhs[2]))
libsvmwrite(filename, prhs[1], prhs[2]);
else
{
mexPrintf("Instance_matrix must be sparse\n");
return;
}
}
else
{
exit_with_help();
return;
}
}
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