I is not a real numeric array of class SINGLE

Question

I'm using the computer vision: VLfeat library to compute a HOG descriptor of an image, and after inputing this code:

cellSize = 8 ;
hog = vl_hog(im, cellSize, 'verbose') ;

I get this error in MATLAB, and when I google it I really can't find any possible explanation:

Error using vl_hog
I is not a real numeric array of class SINGLE.

After going over the code (found here) I'm also not sure what the variable I is:

Hopefully, I haven't missed something elementary ...

library source

Answer 1

As the asker already found out, the I refers to the first input argument. Hence this should solve the problem:

hog = vl_hog(single(im), cellSize, 'verbose')