index problem while sort

I am trying to sort some positive values from one array and finding the index of that.

Omega=[1.528 -1.528 0.792 -0.792];
[NN,ind]=sort(Omega(Omega>=0));

Answer:

NN=[0.792 1.528]

but

ind=[2,1] is coming which is wrong. It should ind=[3,1].

Please help regarding this.

Answer 1

[Dyuman Joshi]

"ind=[2,1] is coming which is wrong."

It is correct.

The input to sort() only has 2 elements, so the expectation to get [3 1] as the output is misplaced -

Omega=[1.528 -1.528 0.792 -0.792];
Omega(Omega>=0)

ans = 1×2

1.5280 0.7920

I assume you want to get the indices of these particular values from the original array, in that case, try this -

NN=sort(Omega(Omega>=0))

NN = 1×2

0.7920 1.5280

[~,idx] = ismember(NN,Omega)

idx = 1×2

3 1

Ideally, you should use ismembertol to compare floating point numbers.

However, the values here are obtained directly from the original array via indexing, so ismember() works here.

[VINAY PRAJAPATI]

Thank you so much sir for solving the problem.

Answer 2

[VBBV]

Here is another way to get the indices without overhead of using ismember function

Omega=[1.528 -1.528 0.792 -0.792];
[NN,ind]=sort(Omega)

NN = 1×4

-1.5280 -0.7920 0.7920 1.5280

ind = 1×4

2 4 3 1

ind(NN>0)

ans = 1×2

3 1