Matlab is plotting something--only the last value in the loop. To get the results with a loop, I suggest this solution:
N = (5:5:85);
p = NaN(size(N)); % preallocate to speed things up
for n = 1:length(N)
r = 0.15;
l = 50000;
p(n) = [r * l * (1 + r/12)^(12 .* N(n) )/ (12 * ((1+r/12)^(12 .* N(n)) - 1 ))];
% x = [N(1): N(end)];
% y = [p(1) : p(end)];
% disp( [ N p]);
format bank
end
plot(N,p)
However, I think the loop is unnecessary (loops tend to slow things down). I'd prefer this simpler solution instead:
N = (5:5:85);
r = 0.15;
l = 50000;
p = r * l * (1 + r/12).^(12 .* N )./ (12 * ((1+r/12).^(12 .* N) - 1 ));
plot(N,p,'r')
