The arguments you use for 'randfixedsum' are rather strange! It is the columns whose sum must be 5 and your columns have only one element, so that element must be 5. There would be nothing randome about it. You could just as well have written:
repmat(5,1,4)
or
5*ones(1,4)
To get a row vector whose sum is 5, take the transpose of a 4 by 1 vector:
randfixedsum(4,1,5,0,5).'
As to the error message, it looks as though you haven't downloaded that file exchange function properly. Try again. Click on the button that says, "Download Submission".
