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choose elements from list based on elements in different list
*To*: mathgroup at smc.vnet.net
*Subject*: [mg86707] choose elements from list based on elements in different list
*From*: Claus <clausenator at gmail.com>
*Date*: Wed, 19 Mar 2008 05:23:33 -0500 (EST)
*Organization*: Comp.Center (RUS), U of Stuttgart, FRG
Hi,
I'm trying to choose elements from list based on elements in different
list and I came up with the ideas listed below. It seems to me that
there are a few too many steps involved here, and I need to run this on
larger lists (~20000 entries).
Are there ways to improve this?
Thanks,
Claus
Here is the mathematica code:
Reihe1={22,33,44,0,0,16,5,0,0,0}
Reihe2={16,27,0,0,5,11,5,0,0,12}
{22, 33, 44, 0, 0, 16, 5, 0, 0, 0}
{16, 27, 0, 0, 5, 11, 5, 0, 0, 12}
(*Find out where in Reihe1 and in Reihe2 are Zeros and notZeros*)
Reihe1Is0 = Thread[Reihe1 == 0]
Reihe1Not0 = Thread[Reihe1 != 0]
Reihe2Is0 = Thread[Reihe2 == 0]
Reihe2Not0 = Thread[Reihe2 != 0]
{False, False, False, True, True, False, False, True, True, True}
{True, True, True, False, False, True, True, False, False, False}
{False, False, True, True, False, False, False, True, True, False}
{True, True, False, False, True, True, True, False, False, True}
(*Select the values of Reihe1 and Reihe2 which are of interest
There are 4 Cases (not all of them calculated later) :
Case1 : Reihe1 and Reihe2 are 0
Case2 : Reihe1 and Reihe2 are NOT 0
Case3 : (Reihe2 is NOT 0) AND (Reihe1 is 0)
Case4 : (Reihe1 is NOT 0) AND (Reihe2 is 0)*)
PreCase3=Pick[Reihe2,Reihe1Is0]
PreCase4=Pick[Reihe1,Reihe2Is0]
{0, 5, 0, 0, 12}
{44, 0, 0, 0}
Case3=Select[PreCase3,#>0&]
Case4=Select[PreCase4,#>0&]
{5, 12}
{44}
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