How to restrict input to set of sizes in an arguments block?

I have a function with argument that should be either 2 x N or 3 x N size. Can't seem to figure out how to have that in an input block. Something similar to below (which isn't supported syntax):

arguments
    myArg (2:3,:);
end

Answer 1

[Steven Lord]

I don't believe you can do this with the dimension validation alone. Nor would the existing validation functions help. So you're going to need to write your own, which I've done below as mustHaveTwoOrThreeRows. These first two cases work:

sample1674659(ones(2, 3))

ans = 6

sample1674659(ones(3, 3))

ans = 9

Specifying an input with the wrong number of rows will error, as will specifying an N-dimensional array (N > 2) (because of the dimension validation.)

try
    sample1674659(ones(4, 3))
catch ME
    fprintf("This case threw the error:\n\n%s\n", ME.message)
end

This case threw the error:

Invalid argument at position 1. X must have either two or three rows.

try
    sample1674659(ones(2, 3, 4))
catch ME
    fprintf("This case threw the error:\n\n%s\n", ME.message)
end

This case threw the error:

Invalid argument at position 1. Value must be a matrix.

function y = sample1674659(x)
arguments
    x (:, :) {mustHaveTwoOrThreeRows(x)}
end
y = sum(x, 'all');
end

function mustHaveTwoOrThreeRows(x)
s = size(x, 1);
if ~(s == 2 || s == 3)
    error('X must have either two or three rows.');
end
end