How to implement the arguments validation in a function correctly?

Hello!!

I am writing a code for neural networks where the user can choose if he wants to use a filter, how many layers, the activation functions to use, etc. I wanted to set an argument validation so the only options the user can choose are already defined. I tried to write it this way but I always get an error. Any sugestion on how to fix it? Thank you!

The error i get is the following:

>> Error using cell/ismember

Input A of class double and input B of class cell must be cell arrays of character vectors, unless one is a character vector.

Error in mustBeMember (line 14)

if ~all(ismember(A, B), 'all')

Error in main (line 12)

nLayers (2,:) double {mustBeMember(nLayers,{1,2})}

>>

function main(filter,nLayers,activFunction1,activFunction2,softmax,testOrTrain)
arguments
    filter (1,:) string {mustBeMember(filter,{'no','AM','BP'})}
    nLayers (2,:) double {mustBeMember(nLayers,{1,2})} 
    activFunction1 (3,:) string {mustBeMember(activFunction1,{'-','hardlim','purelin','logsig'})}
    activFunction2 (4,:) string {mustBeMember(activFunction2,{'hardlim','purelin','logsig'})}
    softmax (5,:) string {mustBeMember(softmax,{1,2})}
    testOrTrain (6,:) string {mustBeMember(testOrTrain,{'train','test'})}
end

... % function itself
end

Answer 1

[Vinayak Choyyan]

Hi,

As per my understanding, you are trying to use Function Argument Validation and you are getting the error you are mentioned above.

Please try the following code snippet:

function main(filter,nLayers,activFunction1,activFunction2,softmax,testOrTrain)
arguments
    filter (1,:) string {mustBeMember(filter,{'no','AM','BP'})}
    nLayers (2,:) double {mustBeMember(nLayers,[1,2])}   %change here
    activFunction1 (3,:) string {mustBeMember(activFunction1,{'-','hardlim','purelin','logsig'})}
    activFunction2 (4,:) string {mustBeMember(activFunction2,{'hardlim','purelin','logsig'})}
    softmax (5,:) double {mustBeMember(softmax,[1,2])}   %change here
    testOrTrain (6,:) string {mustBeMember(testOrTrain,{'train','test'})}
end
... % function itself
end

You were using {1,2} which creates a cell array. I believe you intended to use [1,2] which creates and array. I also changed the data type from string to double for softmax. You can read more about Function Argument Validation

https://in.mathworks.com/help/matlab/matlab_prog/function-argument-validation-1.html

and check out some examples of using mustBeMember

https://in.mathworks.com/help/matlab/ref/mustbemember.html