OpenCV PCA not initializable

Question

Given http://docs.opencv.org/modules/core/doc/operations_on_arrays.html

PCA should be initializable by just passing it a matrix.

cv::Mat matrix;
...
//If I do
cv::PCA pca;
pca(matrix);

I get the error, that function cv::PCA::operator() cannot be called with the given arguments

And if I do:

cv::PCA pca(matrix);

it says "no instance of constructor matches the argument list"

And if I do:

pca.operator(matrix);

It says "Error: expected an operator". What is going wrong?

Answer 1

"PCA should be initializable by just passing it a matrix."

• no, not true.

there is neither a single-Mat constructor, nor a single-Mat operator().

you have to supply a data-Mat, a mean-Mat and some flags at least.