How to choose all other indices than ones I know?

Hello.

If have an array

a = [11 12 13 14 15]

and I know that I want to change every other indice to NaN apart from indices 2 and 3. How do I do this?

I tried

a(~[2,3]) = NaN;

but it does not do anything. Thanks!

Answer 1

[Birdman]

a(setdiff(1:numel(a),2:3))=NaN

Answer 2

[Jos (10584)]

Here are two options

a = [11 12 13 14 15]
i = [2 3]

b1 = nan(size(a))
b1(i) = a(i)

b2 = a
i2 = setdiff(1:numel(a),i)
b2(i2) = nan

Answer 3

[Jan]

While setdiff is the nicer solution, it has a remarkable overhead. Logical indexing is usually faster:

a            = 1:10;
index        = true(size(a));
index([2,3]) = false;
a(index)     = NaN;