Complement subset in Matlab

Question

In R, I can do the following:

v <- 11:20
v[-(4:5)]

and get 11 12 13 16 17 18 19 20, thus all indices except the 4th and 5th.

Is there an equivalent in Matlab's indexing logic?

However I wrap my mind around it, I do not seem to get the correct search terms to google my own result for this fairly elementary question.

Note: Of course I might use some of the set functions, e.g.

v = 11:20;
v(setdiff(1:length(v), 4:5))

However, this just is not intuitive.

Yes, it works. But is there something more elegant (and maybe more performant)? — Thilo, Mar 13 '13 at 09:22
For clarification: Does `v[-(4:5)]` remove the elements 4 and 5 or the fourth and fifth element? — H.Muster, Mar 13 '13 at 09:24
Oops, yes, that is undefined in my question. It is supposed to remove the fourth and fifth element. Edited the question. — Thilo, Mar 13 '13 at 09:25
Great, I just casted my first close vote. And that own my own question. Is this a good or bad sign? ;) — Thilo, Mar 13 '13 at 09:42
That's a great sign. It means that you care about keeping SO clean and helpful :) BTW doesn't casting close votes require 3K rep? — Eitan T, Mar 13 '13 at 09:55

score 3 · Accepted Answer · answered Mar 13 '13 at 09:25

3

An alternative is to simply remove the elements from the array:

u = v;
u(4:5) = [];

I'm using a temporary variable since I don't know if it's acceptable to modify the original array v or not.

answered Mar 13 '13 at 09:25

Eitan T

Yep, this in fact is a - actually quite obvious - way to do it. Probably the way to go. However, at the cost of an additional copy. – Thilo Mar 13 '13 at 09:29
You don't have to use a copy, if you're okay with modifying `v` itself. – Eitan T Mar 13 '13 at 09:30

score 0 · Answer 2 · answered Mar 13 '13 at 09:25

0

I don't think there is an elegant way, but a more performant might be

v = rand(1,10);
sel = true(1, numel(v));
sel( 4:5 ) = false;
v = v( sel );

answered Mar 13 '13 at 09:25

Shai

2 Answers2