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Re: confused multiplying arrays [message #73558 is a reply to message #73482]

Fri, 12 November 2010 06:30

David Gell
Messages: 29
Registered: January 2009

Junior Member

On Nov 11, 3:11 pm, Paula <paulartcoe...@gmail.com> wrote:
> hello,
>
> i've got two arrays:
>
> IDL> help,area,fluxes
> AREA FLOAT = Array[2000]
> FLUXES FLOAT = Array[2000, 112864]
>
> I want the i-th element in area AREA[i] to multiply all elements in
> the corresponding 2nd dimension in fluxes FLUXES[i,*] and then sum up
> all the 2000 resulting fluxes, i.e., using loop:
>
> for i = 0,1999 do begin
> TOTAL_FLUX = TOTAL_FLUX + AREA[i]*reform(FLUXES[i,*])
> endfor
>
> i've been trying to figure out (without success) how to compute
> TOTAL_FLUX without the loop using TOTAL(). ideas?
>
> thx
> p.

Use the matrix multiply operator, TOTAL_FLUX=TOTAL(AREA # FLUXES).

IDL can be a little confusing about matrix multiplication. It has two
operators # and ## that perform the operation.
A#B = B##A.

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[Message index]

		confused multiplying arrays By: paulartcoelho on Thu, 11 November 2010 13:11
		Re: confused multiplying arrays By: penteado on Fri, 12 November 2010 08:21
		Re: confused multiplying arrays By: paulartcoelho on Fri, 12 November 2010 08:10
		Re: confused multiplying arrays By: David Gell on Fri, 12 November 2010 06:30

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