Index in position 1 exceeds array bounds.

I got an error while trying to run this code , this command occurs Index in position 1 exceeds array bounds.

Happy = [trainf(1,:);trainf(3,:);trainf(5,:);trainf(6,:);trainf(15,:);trainf(16,:)];

When running trainf in command window I get

trainf =

[ ]

and when running rref i get

Not enough input arguments.

Error in rref (line 23)

[m,n] = size(A);

how can I fix this error

[dpb]

By defining trainf first before trying to use it, may be a starting point...

[DGM]

You don't mention how you're calling rref(), but from the error, it seems you're calling it with no arguments. If you want to find the rref of a matrix, you actually have to specify one.