"Matrix dimensions must agree"

Matrix dimensions must agree

Answer 1

[Massimo Zanetti]

Of course it gives you an error. In your script

x=0:0.01:6

is a vector of size 1x601. When you do elementwise multiplication

M=eye(3).*x;

you are trying to multiply a 3x3 matrix with a 1x601 vector, which is impossible.

[Massimo Zanetti]

To obtain the graph of y=3x just do this:

x = 0:0.01:6;
y = 3*x;
plot(x,y);

You don't need to go through matrix multiplication in Matlab for elementwise multiplication of a vector (or a matrix) with a scalar.