MathLab 2019 backward compatibility

The following code compiles and runs fine in '9.7.0.1216025 (R2019b) Update 1'

function approx = test3(x,N)
    approx = zeros(N,1);
    approx(1) = x + 1;
    for i = 2:N
        approx(i) = approx(i - 1) + x^i / factorial(i);
    end
end

However, when I try and run it in my 2017 Uni environment, I get the following error:

Output argument "output" (and maybe others) not assigned
during call to "factorial".
 
Error in test3 (line 5)
    approx(i) = approx(i - 1) + (x^i) / factorial(i);

Any ideas please?

Answer 1

[J. Alex Lee]

is it possible that in your 2017 environment, you have inadvertently overloaded the "factorial" function?

[andrew boar]

Thank you for the prompt response.

I doubt that is the answer though as we are running the routine with parameter N set to 5.

Typical test data is:

test3(1.5, 5)

!5 = 120 so that doesnt sound like an overload situation?

[Sean de Wolski]

Overloading as in there are multiple files named factorial.m

What is the output of

which -all factorial

Rename any that aren't base in matlabroot.

[andrew boar]

I have to say, I do have a number of years experience with many high level languages, but i am very new to MathLab. Are you saying that MathLab has access to four versions of factorial.m and does not know which one to use?

This output is from the 2017 environment.

>> which -all factorial

C:\Users\ttssb2\OneDrive - My University\MATLAB\factorial.m

C:\Program Files\MATLAB\R2017a\toolbox\distcomp\parallel\@codistributed\factorial.m % codistributed method

C:\Program Files\MATLAB\R2017a\toolbox\distcomp\gpu\@gpuArray\factorial.m % gpuArray method

C:\Program Files\MATLAB\R2017a\toolbox\symbolic\symbolic\@sym\factorial.m % sym method

C:\Program Files\MATLAB\R2017a\toolbox\matlab\specfun\factorial.m

[Sean de Wolski]

Yes. This is the default one that ships with MATLAB that you're probably intending to call but aren't:

C:\Program Files\MATLAB\R2017a\toolbox\matlab\specfun\factorial.m

The other three in matlabroot are overloaded ones for those specific data types. The one in OneDrive is shadowing the specfun one that you're intending to call. Rename the OneDrive one to myFactorial or something to avoid the conflict.

[andrew boar]

Many thanks.

I can confirm this had completely resolved the issue.

Brilliant!