MATLAB: Using conditional statements inside cellfun

Question

Suppose I have two cell arrays X and Y. If Y{i} satisfies a condition, I want to transform X{i} into some X'{i}, otherwise leave X{i} unchanged. Something like:

for i=1:N
    if Y{i}>2, X_out{i} = reshape(X_in{i},...);
    else X_out{i} = X_in{i}; end
end

How can I do this with cellfun? Multiplying by false won't work because the transformation involves reshaping X{i}. For example, the following doesn't work:

X_out = cellfun(@(x,y) ~(y>2)*x + (y<=2)*reshape(x,...), X_in, Y);

I presume this question applies to anonymous functions in general.

Answer 1

You cannot use those kinds of conditionals in cellfun, at least not without the use of an auxillary true function that does the equivalent of the C/C++ question-colon operator.

The workaround is

mask = cellfun(@(y) y>2, Y);
X_out = X_in;
X_out(mask) = cellfun(@(xin) reshape(xin, ...), X_in(mask), 'uniform', 0);