Problems with your code
- A(i) outputs a scalar. You want A(:,i), which outputs the i:th column
- your code displayed a dot, which was difficult to see
Try
X=1:1:100;
A=randi([1 10],100,3);
B=A+2;
%
for i=1:3
subplot(3,1,i)
plot(X,A(:,i));
hold on
plot(X,B(:,i));
hold off
end
which creates
