How to display unique error message in function code?

Here is my code:

function returnVec = repvec(vec, s)
    returnVec = [];
    i = 1;
    for x = vec
        for y = 1:s
            returnVec(i) = x;
            i = i+1;
        end
    end
end

For example, in the command window when I put in repvec([1,2;3,4],2), I get an error message. This is what I wanted to happen and is supposed to occur. However, how do I create my own unique error message such as "The first input argument is invalid!" if any input arguments are incorrect? (This is so that others who use my code can know why they received an error.) I have to use the error function.

[dpb]

What specific is the problem with following an example as shown in the documentation for the error() function? It has examples for the exact purpose.

Answer 1

[Daniel M]

You need to manually check the input arguments yourself. For example:

function returnVec = repvec(vec, s)
  if ~isvector(vec)
    error('vec must be a vector.')
  end

    returnVec = [];
    i = 1;
    for x = vec
        for y = 1:s
            returnVec(i) = x;
            i = i+1;
        end
    end
end