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Re: Finding Common Elements in Two Arrays [message #2167 is a reply to message #2111]

Mon, 06 June 1994 01:09

stl
Messages: 70
Registered: February 1994

Member

Good morning,

My program, where_array() that I posted on friday has a few bugs. I
will modify it with some of the ideas from below.

NOTE: I beleive the below posting has an error in it:

In article <1994Jun3.131050.3790@mksol.dseg.ti.com> landers@tsunami.dseg.ti.com writes:
> It's me again...
>
> Now I noticed you want the indices rather than the values.... So
>
>
> In article <1994Jun3.130243.3453@mksol.dseg.ti.com>, landers@tsunami.dseg.ti.com (David Landers) writes:
>
> |>
> |> Na = N_ELEMENTS(a)
> |> Nb = N_ELEMENTS(b)
> |> L = LINDGEN(Na,Nb)
> |> AA = A( L MOD Na )
> |> BB = B( L / Na )
>
> Then...
>
> I = AA EQ BB
> Ia = UNIQUE( I MOD Na )
^^^
> Ib = UNIQUE( I / Na )
^^^
>
> Now Ia has the indices of A that are in B, and Ib has the indices of B that
> are in A. Leave off the UNIQUE if you care that an element matches multiple
> times.

I believe the above two lines with the unique(i ...) should be as
follows:

Ia = unique(where(i) mod na)
Ib = unique(where(i) / na)

then clearly the common elements are just a(ia) and b(ib)

I will post a more stable routine with these new ideas. This is indeed
better because it should handle string arrays, i too believe it to be
faster.

-stephen Strebel

--
Stephen C Strebel / SKI TO DIE
stl@maz.sma.ch / and
Swiss Meteorological Institute, Zuerich / LIVE TO TELL ABOUT IT
01 256 93 85 / (and pray for snow)

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[Message index]

		Finding Common Elements in Two Arrays By: kucera on Wed, 01 June 1994 13:45
		Re: Finding Common Elements in Two Arrays By: stl on Wed, 01 June 1994 23:26
		Re: Finding Common Elements in Two Arrays By: stl on Mon, 06 June 1994 01:09
		Re: Finding Common Elements in Two Arrays By: landers on Fri, 03 June 1994 06:10
		Re: Finding Common Elements in Two Arrays By: landers on Fri, 03 June 1994 06:02
		Re: Finding Common Elements in Two Arrays By: dan on Wed, 01 June 1994 16:23
		Re: Finding common elements in two arrays By: andy on Tue, 26 July 1994 09:39

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