How can I evaluate a function at a vector and plot the returned values?

Using this function code: function [y1,y2] = f(x1)

y1 = 6*sin(x1) + cos(2*x1)

y2 = 12*sin(2*x1) + cos(4*x1)

end

I need to evaluate it at multiple points using the vector: x1 = linspace(0, 2*pi, 10);

So, I entered this code on my main script:

x1 = linspace(0, 2*pi, 10);

ii = f(x1)

It returns the error: Subscript indices must either be real positive integers or logicals.

Can someone please tell me what I am doing wrong? I know this is basic, but I am new to Matlab and my class on it isn't very helpful.

Answer 1

[Matt J]

First type

 clear f

then re-run.

[Japheth Gielen]

Thanks a lot. I am wondering though why do I have to do that? Also, do I have to do that for every function I evaluate at a vector?

[Matt J]

You had to do it because you had a variable named "f" already existing in the workspace. Avoid conflict between functions and variable names and there will be no need for this.

[Japheth Gielen]

Oh ok I didn't realize. Thanks again for your help.