code for slope and intercept of a straight line

I keep getting "matrix dimensions must agree error" and error in line 2 here's my code below

    % code
x =(-2:0.02:2);
y = (m*x)+b;  <==================================line 2
m = input('enter the slope m');
b = input('enter the intercept b');
subplot(1,1,1)
plot(x,y,'r'), xlabel('x'),ylabel('y'), axis([-2 2 -1 1])

Answer 1

[Image Analyst]

Line 2 needs to come AFTER the m= and b= lines. How else will y know what they are???

[bachir]

thank you