comp.lang.idl-pvwave archive: archive » averaging over same index

Home » Public Forums » archive » averaging over same index

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

averaging over same index [message #45293]

Tue, 23 August 2005 09:22

andi.walther
Messages: 1
Registered: August 2005

Junior Member

Hello,

I have an array V(alues) and an array S(ubscripts of a target array)
and I want to
extract the mean of all values with the same index in order to put them
into the new array.

As a simple example:
V = [ 3, 7, 99, 5, 2 , 10]
S = [ 1, 3, 3, 2 , 0 ,1]

new vector should be --> new = [ 2 , 6.5 , 5, 53 ]

slow way would be: for n = 0 , max(S)-1 do new[n]=mean(v[where(S eq
n)])

a bit faster without WHERE in the loop:

VSorted = v[sort(S)]
SSorted = S[sort(S)]
uu = uniq(iSorted)
for n = 0 , n_elements(uu)-1 do new[iSorted[uu[n]]] =
mean(vSorted[n:(n-1)>0])

But is there a way to do what I want without resorting to
a loop? In my real-world problem I have vectors with 500000 elements
and the number of the occurence of indices
are quite irragular and can exceed 30 times.

Thanks Andi

Report message to a moderator

[Message index]

averaging over same index

By: andi.walther on Tue, 23 August 2005 09:22

Previous Topic:	Cursor problems, MAC and PC
Next Topic:	Re: averaging over same index

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Wed Oct 08 18:25:04 PDT 2025

Total time taken to generate the page: 0.00439 seconds