Re: choose elements from list based on elements in different list

*To*: mathgroup at smc.vnet.net*Subject*: [mg86755] Re: choose elements from list based on elements in different list*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Thu, 20 Mar 2008 02:54:30 -0500 (EST)*Organization*: Uni Leipzig*References*: <frqpnb$4vl$1@smc.vnet.net>*Reply-to*: kuska at informatik.uni-leipzig.de

Hi, Reihe1 = {22, 33, 44, 0, 0, 16, 5, 0, 0, 0}; Reihe2 = {16, 27, 0, 0, 5, 11, 5, 0, 0, 12}; try for "PreCase3" Last /@ Select[Transpose[{Reihe1, Reihe2}], #[[1]] == 0 &] and First /@ Select[Transpose[{Reihe1, Reihe2}], #[[2]] == 0 &] for "PreCase4" Regards Jens Claus wrote: > 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} >