normal different sigma

x = -10:0.1:10;
mu = 3;
sigma1 = 2;
sigma2 = 3;
sigma3 = 1;

y1 = normpdf(x,mu,sigma1);
y2 = normpdf(x,mu,sigma2);
y3 = normpdf(x,mu,sigma3);

plot(x,y1,'r');
hold on;
plot(x,y2,'g');
plot(x,y3,'b');
title('NORMAL DISTRIBUTION CURVE FOR DIFFERENT SIGMA');
legend('sigma=2','sigma=3','sigma=1');