How to get the opposite elements of a vector specified by an index?

I have a variable s picking 70 random numbers from 0 to 100. Now I want to have all 30 elements of the vector a, which are not in s.

s = randsample(100,70)

I have already tried

    z = a(~s)

but that does not work.

Answer 1

[Rik]

randsample picks values from 1 to N, not 0 to N. The first block is for 1:N, the second for 0:N

maxval=100;
s = randsample(maxval,70);
not_s=1:maxval;not_s(s)=[];

maxval=100;
s = randsample(maxval+1,70);
not_s=1:maxval;not_s(s)=[];
not_s=not_s-1;s=s-1;

[Stef]

Thanks! I needed it for the 1:N. Could you please explain the intuition? I do not understand why it picks exactly the opposite ones now

[Rik]

What this code does is generating the vector 1:N and then removing all positions described by s. This makes use of the fact that position and value is the same in the vector that results from 1:N.