Re: AppendTo VERY slow
- To: mathgroup at smc.vnet.net
- Subject: [mg35306] Re: [mg35279] AppendTo VERY slow
- From: BobHanlon at aol.com
- Date: Mon, 8 Jul 2002 03:15:36 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
In a message dated 7/6/02 6:53:23 AM, M.P.Croucher at Sheffield.ac.uk writes: >I use lists a lot in mathematica and tend to use AppendTo[] a lot in >my programs. Recently I wrote a function that i call over and over >again and found that the results were coming very slowly and i MEAN >slowly. I was doing Fourier Transforms and all kinds of stuff so I >put it down to those at first but I have just put in a load of Print >statements just after each part of the function to see what was taking >so long. > >I was amazed to see that the Fourier Transforms were so quick and what >was actually taking the time was a part of my function that collected >the results togther in the form I wanted and outputted the result. It >looks like this > >Do[ > elem = {xlist[[count]], ylist[[count]]]}; > AppendTo[outlist, elem]; > , {count, 1, number} > ]; > >It seems that as the list grows it gets slower and slower. Any tips >on a way around this would be greatly appreciated (would speed my life >up no end) Use either Transpose[{xlist, ylist}] or Thread[{xlist, ylist}] Bob Hanlon Chantilly, VA USA