find duplicate values, sort them and get their indices

Suppose i have 3 arrays:

Position=[ 15 15 15 15 15 15 15 15 15 15 16 16 16 16 16 16 16  17 18 18 18...]
Ray=[1 2 3 1 1 1 2 2 2 3  1 2 4 4 4 4 2 2 4 5 5...]
and Amplitude=[0.1 0.2 0.15 0.02 0.25 0.06 0 0.01 0.7 0.25 0.315 0 0.45 0.2 0.1 0.1 0.8 ...]

How can i get the rays corresponding to the position==15 (Here:

Ray(Position==15)=[1 2 3 1 1 1 2 2 2 3]),  sort them in order to get Ray'(Position==15)= [1 1 1 1 2 2 2 2 3 3] and then extract the corresponding amplitudes [0.1 0.02 0.25 0.06 0.2 0 0.01 0.7 0.15 0.25].

Any solution to this please? Thank you in advance for your help

Answer 1

[Adam]

rayPos15 = Ray( Position == 15 );
ampPos15 = Amplitude( Position == 15 );

[sortedRayPos15, idx] = sort( rayPos15 );
sortedAmpPos15 = ampPos15( idx );

There's probably a neater way to do it, but something like that should give the result you want I think

Answer 2

[Joakim Magnusson]

It's hard to understand what you mean, but here's my guess. if you do this:

tempV = Position==15;
tempV = sort(Ray(tempV));

Then tempV will look like this:

tempV = [1 1 1 1 2 2 2 2 3 3];

Is that of any help?

I couldn't understand how or why you want to get amplitudes [0.1 0.02 0.25 0.06 0.2 0 0.01 0.7 0.15 0.25]?

[F Z]

Actually it is! thank you a lot! But how can i get the amplitudes corresponding to the sorted tempV?

Thank you in advance

[Joakim Magnusson]

do you mean like this?

ampPos15 = sort(Amplitude(tempV));

Will give this i think:

ampPos15 = [0 0.0100 0.0200 0.0600 0.1000 0.1500 0.2000 0.2500 0.2500 0.7000];

[F Z]

In fact, what i want to do is to get the amplitudes corresponding to the sorted TempV= [[1 1 1 1 2 2 2 2 3 3] that are [0.1 0.02 0.25 0.06 0.2 0 0.01 0.7 0.15 0.25]

Then sum the amplitudes corresponding to each ray: TempV==1, TempV==2 ..etc

Hope that it's getting clearer?!!

Answer 3

[Iain]

This might be what you're looking for:

 Amplitude(Position == 15 & Ray == 1)

Ot maybe:

 RayNumbers = Ray(Position == 15);
URayNumbers = unique(RayNumbers);

 URayNumbers(1)
 Amplitude(Position == 15 & Ray == URayNumbers(1))

[F Z]

Thank you all for your answers. I'll try to do it in a loop for each position