Matlab grader not working

I have setup a test in Matlab grader, my reference solution contains a variable called finalvalue (you find the code at the end of this message). I want to assess the student on the value of finalvalue. So I am using in the assessment panel the option to verify the value of final value. I test the reference code and I obtain

Unable to resolve the name referenceVariables.finalvalue. Error in Test1

I have also tried to do the check explicitely with

xReference = referenceVariables.finalvalue;
assessVariableEqual('finalvalue', xReference);

with no avail!! It seems that the grader is unable to find the variable (I have event tried to change the variable name.... same error).

Her the code (which workd perfectly, it produces the right plot and the right value of finalvalue (rk4.m is a script which is provided in the File Referenced section and is a simple runge kutta).

Could you explain me what I am doing wrong?

Here is the code:

clear all
close all
%%
mu=10;
f = @ (t,y) [y(2);mu*(1-y(1)^2)*y(2)-y(1)];
y0=[0;10];
tspan=[0,100];
%%
h=0.01;
Nh=(tspan(2)-tspan(1))/h;
[t,u]=rk4(f,tspan,y0,Nh);
%
plot(t,u(:,1),t,u(:,2));
figure
plot(u(:,1),u(:,2));
%%
finalvalue=u(end,2);
finalvalue

Answer 1

[Luca Formaggia]

Sorted it out! It was the

clear all

at the beginning that was causing the problem. After taking it out everything works as expected.

[Sachin Kelkar]

I'm a TA and I spent 1hr looking for bugs, this fixed it. thank you very much!