I want to write a eigenface program using C++ with OpenCV

void doPCA()
  {
          int i;
          CvTermCriteria calcLimit;
          CvSize faceImgSize;

          // set the number of eigenvalues to use
          nEigens = nTrainFaces-1;

          // allocate the eigenvector images
          faceImgSize.width  = faceImgArr[0]->width;
          faceImgSize.height = faceImgArr[0]->height;
          eigenVectArr = (IplImage**)cvAlloc(sizeof(IplImage*) * nEigens);
          for(i=0; i<nEigens; i++)
                  eigenVectArr[i] = cvCreateImage(faceImgSize, IPL_DEPTH_32F, 1);

          // allocate the eigenvalue array
          eigenValMat = cvCreateMat( 1, nEigens, CV_32FC1 );

          // allocate the averaged image
          pAvgTrainImg = cvCreateImage(faceImgSize, IPL_DEPTH_32F, 1);

          // set the PCA termination criterion
          calcLimit = cvTermCriteria( CV_TERMCRIT_ITER, nEigens, 1);

          // compute average image, eigenvalues, and eigenvectors
          cvCalcEigenObjects(
                  nTrainFaces,
                  (void*)faceImgArr,
                  (void*)eigenVectArr,
                  CV_EIGOBJ_NO_CALLBACK,
                  0,
                  0,
                  &calcLimit,
                  pAvgTrainImg,
                  eigenValMat->data.fl);

          cvNormalize(eigenValMat, eigenValMat, 1, 0, CV_L1, 0);
  }