Avoid evaluation in vectorised conditional expressions
2 views (last 30 days)
It is well known how to vectorise for-loops that contain if-conditions, see, e.g. https://de.mathworks.com/matlabcentral/answers/17737-how-can-i-vectorize-function-with-if-statement, resulting in functions like (taken from above link):
function result = myfunc(x);
result = zeros(size(x));
idx1 = x>3;
idx2 = (x.^2 + x) > 9;
result(idx1) = 1;
result(idx2) = 2;
result(~(idx1|idx2)) = 3;
This principle works very well. However, in my case, result(idx1) and result(idx2) would be quite lengthy and expensive expressions. The problem is that both expressions are always evaluated for the entire input x, no matter if idx1 or idx2 are true or not. My question is if there is a way to avoid the evaluation of, e.g., the right hand side of result(idx2) if idx2 is false. Just as it would be in an if-elseif-construct.
I'm aware of alternative constructs with arrayfun or a "classical" for-loop with nested if-elseif-construct, but these workarounds are not efficient.
Any help is much appreciated, thank you!