DATA_AS_ROW       108 samples/cpp/pca.cpp     p->pca = PCA(p->data, cv::Mat(), PCA::DATA_AS_ROW, var);
DATA_AS_ROW       153 samples/cpp/pca.cpp     PCA pca(data, cv::Mat(), PCA::DATA_AS_ROW, 0.95); // trackbar is initially set here, also this is a common value for retainedVariance