How pca() function works in matlab

I'm trying to apply pca() function on 3d data, But I'm getting empty COEFF matrix

x1 = randn(400,1);
y1 = randn(400,1);
z1 = randn(400,1);
plot3(x1,y1,z1,'r.');
[COEFF] = pca([x1;y1;z1]')

Answer 1

[Jason Millen]

The reason you are getting an empty 1200-by-0 matrix is because you are passing a 1-by-1200 matrix to pca.

I believe what you want to do is pass it a 400-by-3 matrix, which can be accomplished with [x1';y1';z1']'. Thus, if you call pca([x1';y1';z1']'), you will get a 3-by-3 coefficient matrix.

If you would like to read up more on the documentation for pca(), you can find it here.

[Walter Roberson]

The user is passing a 1200 x 1 matrix to pca.

[Jason Millen]

I believe there is a transpose operator given before the matrix is passed into pca, making it 1-by-1200. Please correct me if I am wrong.

[Walter Roberson]

Ah, you are correct, I missed that.