Re: AppendTo VERY slow
- To: mathgroup at smc.vnet.net
- Subject: [mg35313] Re: AppendTo VERY slow
- From: "Dana DeLouis" <delouis at bellsouth.net>
- Date: Mon, 8 Jul 2002 03:15:57 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
I am new myself. Would this idea work faster?
x = {1, 2, 3, 4, 5}; y = {a, b, c, d, e};
outlist = Thread[{x, y}]
{{1, a}, {2, b}, {3, c}, {4, d}, {5, e}}
--
Dana
Windows XP & Mathematica 4.1
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"Mike" <M.P.Croucher at Sheffield.ac.uk> wrote in message
news:ag6ed8$bnm$1 at smc.vnet.net...
> 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)
>
>
> Thank
>
> Mike