From that line,
is invalid syntax. If you want element j through the end of the vector, you need
Also, if everything in your code consists of vectors (as opposed to two-dimensional arrays), you don't necessarily need that "1" in your indexing.
would be sufficient. Similarly, if fixsignal is a column vector,
is equivalent to
All variations select all elements of the first column of fixsignal, or in other words the entire signal.
If you pay attention to the size of the variables in Matlab's Workspace panel, it might help you understand future array size error messages (though probably not in this case, if I have correctly pointed out the problem)