Displaying a cell array of strings in a convenient, elegant and robust way

Question

Often, my functions contain a string argument that has a small number of valid options. For example, it might represent a mode similar to the last argument of interp1. When the user passes an incorrect value, I like to give a list of valid options in the error message.

Currently, I solve it like this:

function out = my_func(mode)
valid_modes = {'rectangular', 'gaussian'};
switch mode
    case 'rectangular'
        % do something
    case 'gaussian'
        % do something else
    otherwise
        error(['atmlab:' mfilename ':invalid'], 'Invalid mode: %s. Valid modes: %s', mode, sprintf('%s ', valid_modes))
end

The trick I'm exploiting is that sprintf can take a cell array, and then outputs a concatenation of multiple strings. However, this behaviour appears to be undocumented, and as of Matlab 2012b, Matlabs Code Analyzer has started to warn against this usage of sprintf. It still works, but it might not be a supported way and I don't know if it will remain working in the future, so I'm reluctant to simply ignore or suppress the warning.

Another solution would be to use evalc('disp(valid_modes)'), but that solution makes me puke.

How do I conveniently and elegantly display the value of a cell array of strings?

Answer 1

Since recent versions of Matlab (I think since 2013b), there is a new function strjoin, that joins strings in a cell array. For example:

C = {'Newton','Gauss','Euclid','Lagrange'};  
str = strjoin(C,', ')