MATLAB: Matlab Grader – Determining if a variable is a function handle.

distance_learningMATLABmatlab grader function handle assessmentmatlab_grader

I'm writing a Matlab Grader assignment in which I'd like the students to define a function, say f, as a function handle. I'd then like an assessment test which verifies this. I figured an assessment test in Matlab code which simply said:

isa(f,'function_handle')

would do the job but this registers as true (in Matlab Grader) even when f is not a function handle.

Best Answer

Assessment tests must assert the result. They do not recognize logical results as answers to the test. So the issue is not that false is being marked as correct. The isa(f,'function_handle') is returning false. It is that no assert has told Grader the result is incorrect.

Put another way, assessment tests are correct unless the code returns an error. Assert throws an error if the condition is false. So does the built-in assessVariableEqual function.

Related Solutions

MATLAB: Is it possible to suppress the default error message of the function assessVariableEqual

There is currently no way to suppress the default feedback when using the built-in assessment function assessVariableEqual. The alternative is to instead perform the grading using assert statements. Assert will only show the message you provide (see tips below for more).

To duplicate the behavior of assesVariableEqual, you must

First determine if the student variable exists.
Next, determine if the student variable is the same data type as the reference variable.
Then determine if the student variable is the same size as the reference variable.
Finally, determine if all the values in the student variable are the same as the values in the reference variable. For numeric values, apply a tolerance.

The first 3 tests are necessary to ensure the values can be compared without causing an error.

Here's an example (untested):

% does variable f exist?
assert(exist('f')==true,'The submission must contain a variable named f')
% is f a double?
assert(isa(f,'double'),'Variable f must be of data type double.')
% check size
assert(all(size(f)==size(referenceVariables.f)),'Variable size is incorrect');
% Check values using assert
assert(all(abs(f-referenceVariables.f)<0.0001),'The variable f contains an incorrect value');

MATLAB: I just want to know the reason why the integral function doesn’t work this way

You have to convert the symbolic function to a function-handle that returns a scalar double. You can do this for your example problem:

F = matlabFunction(f);
q = integral(F,0,1);

The first step converts the symbolic expression into a matlab-function-handle.

HTH

Best Answer

Related Solutions

MATLAB: Is it possible to suppress the default error message of the function assessVariableEqual

MATLAB: I just want to know the reason why the integral function doesn’t work this way

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