function str = randstr(N)
% function str = randstr(N)
% 
% generates a str of random characters length N.  Set is alpha-numeric with
% caps.

S = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';

n = 1 + round(rand(1,N)*(length(S)-1));

str = S(n);