Compute quantile of input matrix for given value range from 0.0 to 1.0

cvquantile.cpp

/**
 * compute quantile of input matrix for given value range from 0.0 to 1.0
 */
float cvQuantile(CvMat * src, float p)
{
  p=MIN(1,MAX(0,p)); // eliminate overflow
  int nr = src->rows, nc = src->cols;
  CvMat * converted = cvCreateMat(nr,nc,CV_32F);
  CvMat * reshaped = cvCreateMat(1,nr*nc,CV_32F);
  CvMat * sorted = cvCreateMat(1,nr*nc,CV_32F);
  cvConvert(src,converted);
  memcpy(reshaped->data.ptr,converted->data.ptr,sizeof(float)*nr*nc);
  cvSort(reshaped,sorted,0,CV_SORT_ASCENDING);
  float retval = sorted->data.fl[cvRound(p*(nr*nc-1))];
  cvReleaseMat(&converted);
  cvReleaseMat(&reshaped);
  cvReleaseMat(&sorted);
  return retval;
}