Re: choose elements from list based on elements in different list
- To: mathgroup at smc.vnet.net
- Subject: [mg86886] Re: choose elements from list based on elements in different list
- From: "Dana DeLouis" <dana.del at gmail.com>
- Date: Tue, 25 Mar 2008 01:16:12 -0500 (EST)
"Claus" <clausenator at gmail.com> wrote in message news:frqpnb$4vl$1 at smc.vnet.net... > 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} Hi. Just another option would be to combine the two lists into an integer.(0,1,2,or 3) Reihe1 = {22, 33, 44, 0, 0, 16, 5, 0, 0, 0}; Reihe2 = {16, 27, 0, 0, 5, 11, 5, 0, 0, 12}; ptn = 2*DiscreteDelta /@ Reihe1 + DiscreteDelta /@ Reihe2 {0, 0, 1, 3, 2, 0, 0, 3, 3, 2} Pick[Reihe2, ptn, 2] {5, 12} Pick[Reihe1, ptn, 1] {44} -- HTH :>) Dana DeLouis Mathematica 6 But reading 5.2 Help. :>(