Need help writing function taking matrix as input (linear algebra/matlab)

This is only one part of a larger assignment, but I hope I can make it clear. The problem is as follows:

Write a matlab function ranking(A) which returns a score vector x (basically means solve Mx=x) for the nxn matrix M defined by:

M=(1-m)A+mS

when the input matrix A is a nxn stochastic (means that all entries are non-negative and the sum of all columns add up to one) link-matrix (in our hypothetical web no webpages can have link to themselves) where m=0.15 and S is a nxn matrix where all the entries are 1/n

If A is non-stochastic, the function should return an error message

If this didn't make any sense, hopefully you will get the idea when you see some of my scribbling:

function x = ranking(A)

    n=size(A,1);
    for k=1:n
        s=sum(A(:,k))
        if s~=1
            fprintf('Input must be a stochastic matrix' );
        end
        if (A(k,k)~=0)
            fprintf('Input must be a stochastic matrix' );
        end
        for e=1:n
            if A(e,k)<0
                fprintf('Input must be a stochastic matrix' );
            end
            if A(e,k)>1
                fprintf('Input must be a stochastic matrix' );
            end
        end
    end
    S=ones(n)*(1/n);
    M=(0.85)*A+(0.15*S);
    x=rref(M)

This is just some idea of how it might look like. I couldn't figure out how to make a function take a matrix as input

If anyone will care to help me out I will be grateful

[James Tursa]

I don't understand. The argument A can be anything you want, including a matrix. Just pass a matrix as an argument and it will be a matrix inside the function.

Also, some of your comparison tests could be problematic due to floating point inaccuracies. E.g.,

        s=sum(A(:,k))
        if s~=1

It could be that the sum gets calculated as very close to, but not exactly equal to, 1. So this test could be coded better using a tolerance.