function [capital,interest]=compound(capital,years,rate,timescomp);
% COMPUND: function to compute the compounded capital and the interest.
% call syntax;
%       [capital,interest]=compound(capital,years,rate,timescomp);
%
x0 = capital; n = years; r = rate; k = timescomp;
if r>1 | r<0 | x0<0 | n<0 | k<0    % check for common mistakes
error('Your input must be positive. Also check your interest rate. For 5% enter .05, not 5.')
else
capital = x0*(1+r/k)^(k*n);
interest = capital - x0;
end;