| Re: array addressing [message #2514] |
Tue, 02 August 1994 02:44 |
sjt
Messages: 72
Registered: November 1993
|
Member |
|
|
Terry Kucera (kucera@stars.gsfc.nasa.gov) wrote:
: In article <CtvMnL.MAD@hpl.hp.com>, peter@hpl.hp.com (Peter Webb) writes...
: >William Thompson (thompson@orpheus.gsfc.nasa.gov) wrote:
: >: kump@morph.ebme.cwru.edu (Kenneth S. Kump) writes:
: >
: >: >Just a quick question:
: >
: >: >A=indarr(10,5)
: >: >B=[0,0,1,0,1]
: >
: >
: >: >I would like array C to consist of only A(*,2) and A(*,4).
: >: >I understand why C=A(*,B) doesn't work, but what is the
: >: >correct way?
: >
: >: Just thinking off the top of my head, one could do something like the
: >: following:
: >
: >: IDL> SZ = SIZE(A) ;Get dimensions of A
: >: IDL> BB = REPLICATE(1,SZ(1)) # B ;Match dims. of B to A
: >: IDL> C = A(WHERE(BB EQ 1)) ;Extract requested data
: >: IDL> C = REFORM(C,SZ(1),TOTAL(B)) ;Rectify dimensions
: >
: >: I haven't actually tried this to confirm that it works, but I think it will.
: >: :^)
: >
: >: Bill Thompson
: >
: >Or, c=a(*,[2,4]) might be a bit easier...
: Or, c=a(*,where(b)) if you don't know b ahead of time.
: Terry Kucera
maybe for safety you might be better with:
locs=where(b,nl)
if (nl ne 0) then c=a(*,locs)
to avoid the risk of having effectively c=a(*,-1) which will crash your
program.
--
James Tappin, School of Physics & Space Research
University of Birmingham
sjt@xun8.sr.bham.ac.uk
"If all else fails--read the instructions!"
O__
-- \/`
|
|
|
|
| Re: array addressing [message #2516 is a reply to message #2514] |
Mon, 01 August 1994 16:49  |
kucera
Messages: 7
Registered: June 1994
|
Junior Member |
|
|
In article <CtvMnL.MAD@hpl.hp.com>, peter@hpl.hp.com (Peter Webb) writes...
> William Thompson (thompson@orpheus.gsfc.nasa.gov) wrote:
> : kump@morph.ebme.cwru.edu (Kenneth S. Kump) writes:
>
> : >Just a quick question:
>
> : >A=indarr(10,5)
> : >B=[0,0,1,0,1]
>
>
> : >I would like array C to consist of only A(*,2) and A(*,4).
> : >I understand why C=A(*,B) doesn't work, but what is the
> : >correct way?
>
> : Just thinking off the top of my head, one could do something like the
> : following:
>
> : IDL> SZ = SIZE(A) ;Get dimensions of A
> : IDL> BB = REPLICATE(1,SZ(1)) # B ;Match dims. of B to A
> : IDL> C = A(WHERE(BB EQ 1)) ;Extract requested data
> : IDL> C = REFORM(C,SZ(1),TOTAL(B)) ;Rectify dimensions
>
> : I haven't actually tried this to confirm that it works, but I think it will.
> : :^)
>
> : Bill Thompson
>
> Or, c=a(*,[2,4]) might be a bit easier...
Or, c=a(*,where(b)) if you don't know b ahead of time.
Terry Kucera
|
|
|
|
| Re: array addressing [message #2517 is a reply to message #2516] |
Mon, 01 August 1994 15:04 |
peter
Messages: 80
Registered: February 1994
|
Member |
|
|
William Thompson (thompson@orpheus.gsfc.nasa.gov) wrote:
: kump@morph.ebme.cwru.edu (Kenneth S. Kump) writes:
: >Just a quick question:
: >A=indarr(10,5)
: >B=[0,0,1,0,1]
: >I would like array C to consist of only A(*,2) and A(*,4).
: >I understand why C=A(*,B) doesn't work, but what is the
: >correct way?
: Just thinking off the top of my head, one could do something like the
: following:
: IDL> SZ = SIZE(A) ;Get dimensions of A
: IDL> BB = REPLICATE(1,SZ(1)) # B ;Match dims. of B to A
: IDL> C = A(WHERE(BB EQ 1)) ;Extract requested data
: IDL> C = REFORM(C,SZ(1),TOTAL(B)) ;Rectify dimensions
: I haven't actually tried this to confirm that it works, but I think it will.
: :^)
: Bill Thompson
Or, c=a(*,[2,4]) might be a bit easier...
|
|
|
|
| Re: array addressing [message #2518 is a reply to message #2517] |
Mon, 01 August 1994 14:06 |
thompson
Messages: 584
Registered: August 1991
|
Senior Member |
|
|
kump@morph.ebme.cwru.edu (Kenneth S. Kump) writes:
> Just a quick question:
> A=indarr(10,5)
> B=[0,0,1,0,1]
> I would like array C to consist of only A(*,2) and A(*,4).
> I understand why C=A(*,B) doesn't work, but what is the
> correct way?
Just thinking off the top of my head, one could do something like the
following:
IDL> SZ = SIZE(A) ;Get dimensions of A
IDL> BB = REPLICATE(1,SZ(1)) # B ;Match dims. of B to A
IDL> C = A(WHERE(BB EQ 1)) ;Extract requested data
IDL> C = REFORM(C,SZ(1),TOTAL(B)) ;Rectify dimensions
I haven't actually tried this to confirm that it works, but I think it will.
:^)
Bill Thompson
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
