Re: Re: Elegant syntax for multiple conditional assignment?

*To*: mathgroup at smc.vnet.net*Subject*: [mg54421] Re: Re: [mg54337] Elegant syntax for multiple conditional assignment?*From*: Scott Hemphill <hemphill at hemphills.net>*Date*: Sun, 20 Feb 2005 00:09:17 -0500 (EST)*Reply-to*: hemphill at alumni.caltech.edu*Sender*: owner-wri-mathgroup at wolfram.com

On Sat, 19 Feb 2005, Bob Hanlon wrote: > a1={1,2,3,4,5}; > c1={6,7,8,9,10}; > x1={11,12,13,14,15}; > y1={16,17,18,19,20}; > > old={a1,c1,x1,y1}; > > a2={21,22,23,24,25}; > c2={26,27,28,29,30}; > x2={31,32,33,34,35}; > y2={36,37,38,39,40}; > > new={a2,c2,x2,y2}; > > cond={True,False,True,False,True}; > > t=Transpose; > > t[If[#[[1]],#[[2]],#[[3]]]&/@t[{cond,t[new],t[old]}]] == > > t[Table[If[cond[[n]],new[[All,n]],old[[All,n]]],{n,Length[cond]}]] > > True > > n=10000; > > old=Table[Random[],{4},{n}]; > > new=Table[Random[],{4},{n}]; > > cond=(Table[Random[Integer,{0,1}],{n}]/.{1->True,0->False}); > > Timing[{a,c,x,y} = > t[If[#[[1]],#[[2]],#[[3]]]&/@t[{cond,t[new],t[old]}]];] > > {0.2 Second,Null} > > Timing[{a,c,x,y} = t[Table[ > If[cond[[n]],new[[All,n]],old[[All,n]]],{n,Length[cond]}]];] > > {0.13 Second,Null} Ah! That's what I was after. Thanks! The timings aren't critical. I was merely looking for something that was simple and obviously correct. I figured that if I asked the group, I would get something better than my solution, and that I would learn something in the process. In this case, I was unaware of the "All" option to "Part". Scott -- Scott Hemphill hemphill at alumni.caltech.edu "This isn't flying. This is falling, with style." -- Buzz Lightyear