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Re: reducing the time of constructing a List


Hi,
try replacing every elemnt different from 1 by zero:

dat /. x_Integer -> 0 /; x != 1

sincerely, Daniel

marloo3 at mail15.com wrote:
> please, what is the best way to reduce the timing of the following lines, the 
> source of data is:
> dat = Table[Random[Integer, {0, 10}], {100000}];
> and the purpose is to construct the List lst in the following way:
> For[i = 1, i <= 100000,
>       If [dat[[i]] == 1,
>         lst = Join[lst, {1}], lst = Join[lst, {0}]]; i++]; // Timing
> 
> Out[]= {226.07 Second, Null}
> on the P4 celeron 2 Ghz , memory 382 MB ram
> thanks
> 


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