It is not entirely clear to me what you try to achieve. If you want to load s from different mat files, you can do so using
function auc=result(data, matfile)
% your code here
load(matfile, 's');
% your code here
And call it using
auc1 = result(mydata, 'karate.mat');
auc2 = result(mydata, 'us.mat');