When using assignin in subfunction A to create a variable in the workspace of subfunction B, the variable is being overwritten by a MATLAB built-in function with the same name

Here is a similar example code. In the original code, there are numerous variables, making it difficult to refactor the code structure or rename variables. I aim to understand the root cause of the error. Specifically, in the example code, even though a variable beta exists in the workspace of subfunction test_beta, MATLAB still recognizes beta as the built-in function. Notably, this issue does not occur when the variable is assigned in the base workspace of the main program.

output = test_beta(10);

Not enough input arguments.

Error in beta (line 19)
y = exp(betaln(z,w));

Error in solution>test_beta (line 6)
output = beta;

function output = test_beta(input)
test_beta2(input)
output = beta;
end


function test_beta2( input )
assignin('caller', 'beta', input);
end

[Stephen23]

"I aim to understand the root cause of the error."

See 3) here:

https://www.mathworks.com/matlabcentral/discussions/tips/849901-tutorial-why-variables-should-not-be-named-dynamically-eval/#reply_2588436

and in the documentation here:

https://www.mathworks.com/help/matlab/import_export/troubleshooting-loading-variables-within-a-function.html

Solution: write better code that does not make variables magically appear without any warning.

Answer 1

[Matt J]

The real solution is this,

function output = test_beta(input)

output = test_beta2(input);

end

function beta=test_beta2( input )

beta=input;

end

but if you must use assignin, you can get around the issue by doing,

output = test_beta(10)

output = 10

function output = test_beta(input)
    beta=[];
    test_beta2(input)
    output = beta;
end


function test_beta2( input )
    assignin('caller', 'beta', input);
end