PCA and project Space

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good afternoon,

I'm trying to project and space, but I have a mistake and I cann't see the fail.

My sumary code is...

PCA pca(InputData, Mat(), CV_PCA_DATA_AS_ROW, NumComponents);
MatPCA= pca.eigenvectors.clone();
for (i=0; i<Data.size(); i++) {
        pca.project(Data[i], compressed);
        OutputData.push_back(compressed);
}
gemm(Data[0], MatPCA, 1, NULL, 0, Out,GEMM_2_T);
printf("Numero %d. diff = %g\n", 0, norm(OutputData[0], Out, NORM_L2));

The result is different from 0 and I don't understand why

Thanks for your help