have a function that returns multiple values, but only use one of them? in matlab

In Matlab, you can return multiple values from a function by separating them with commas. If you only want to use one the output variables, you can use the tilde (~) character to indicate that you don't intend to use that value. Here is an example function that returns three outputs but only the first is used:

main.m
function [output1, output2, output3] = myFunction(input1, input2)
    % some computations 
    output1 = input1 + input2;
    output2 = input1 - input2;
    output3 = input1 * input2;
end
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To use only the first output, you can call the function and assign the outputs like this:

main.m
result = myFunction(2, 3); % returns 5, -1, 6
value = result(1); % assigns the first output (5) to the variable "value"
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Alternatively, you can use the tilde to indicate that you don't care about the other outputs:

main.m
[value, ~, ~] = myFunction(2, 3); % assigns only the first output (5) to "value"
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Note that using the tilde character can be useful if you want to ignore some outputs but still want to maintain the correct number of output arguments.