index exceeds matrix dimensions

I'm having an issue with the following code that models token ring behaviour:

clc
clear all

syms k C W

E(C) = ((50*2.15e-4)/(1-(50*k*2.215e-4)));
E(W) = (((2.637e-8)*(1-0.02215*k + (1.227e-4)*k^2) - (1.15e-4)*(1-0.011075*k))/ (0.0215*(1-0.02215*k + (1.227e-4)*k^2) - (((2.31125e-4)*k)*(1-0.011075*k))));

hold all
fplot(((50*2.15e-4)/(1-(50*k*2.215e-4))))
xlabel('lamda');
ylabel('E(C)');
title('Graph of E(C) against Lamda','FontSize',12);

when this program runs the error 'index exceeds matrix dimensions' appears and states a problem with the line beginning flpot. anyone know how to fix this?

[John BG]

Hi Nick

this is John BG <mailto:[e-mail] [e-mail]>

What version of MATLAB are you using?

With latest release your code works ok:

Answer 1

[Star Strider]

The fplot function is expecting a function and a range for the independent variable.

Try this:

fplot(@(k) ((50*2.15e-4)./(1-(50*k*2.215e-4))), [-1  1])

[Nick]

works! thank you

[Star Strider]

My pleasure!

If my Answer helped you solve your problem, please Accept it!

Answer 2

[Walter Roberson]

The code runs to completion on newer versions of MATLAB. A couple of releases ago, fplot was improved to support symbolic expressions.

However, note that when you define

E(C) = expression1;
E(W) = expression2;

then you are overwriting E with the second statement. The statements are equivalent to

E = symfun(expression1, C);
E = symfun(expression2, W);

The syntax does not define two different functions, E subscript C and E subscript W.

Your fplot does not use either one at the moment though.