Problem in calculating Principal Component Analysis

I am not able to calculate Principal Components of a RGB image without converting it into Gray image,whenever i use princomp function on it, it shows following error :-

Undefined function or method 'svd' for input arguments of
type 'double' and attributes 'full 3d real'.

Error in ==> princomp at 73 [ignore,ignore,coeff] = svd(x0,econFlag);

Please help me out

Answer 1

[Thomas]

princomp performs PCA only on 2D matrices, I'm assuming your image is a 3D matrix of form n x p x m.

doc princomp

princomp(X) performs principal components analysis (PCA) on the n-by-p data matrix X, and returns the principal component coefficients, also known as loadings. Rows of X correspond to observations, columns to variables. COEFF is a p-by-p matrix, each column containing coefficients for one principal component.

here is a link to a similar problem

http://www.mathworks.se/matlabcentral/newsreader/view_thread/259613