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Re: Problem with Position

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  Re: Problem with Position Dominic Wörner <dominic.woerner@mpi-hd.mpg.de> - 2011-06-16 08:00 +0000

#3114 — Re: Problem with Position

Hi Leonid,

Many thanks for your advise but I still have one problem

When I write to a file using WriteString[str, ToString[number]] it will 
be written in OutputForm. Now I thought using your advice It should work 
with Position[..., x_/;x==OutputForm[number]]
but unfortunately it doesn't
Am 15.06.2011 um 12:59 schrieb Leonid Shifrin:

> Hi Dominic,
>
> This is most likely a symbolic/numerical issue. Position is based on 
symbolic rather than numeric comparisons.
> You may have success with
>
> Flatten@Position[data[[All,1]],x_/;x==0.785398]
>
> Here is one of the most recent related discussions:
>
> http://stackoverflow.com/questions/5750623/using-position-correctly
>
> Regards,
> Leonid
>
>
> On Wed, Jun 15, 2011 at 3:20 PM, Dominic W=F6rner 
<dominic.woerner@mpi-hd.mpg.de> wrote:
> Hi,
>
> I have to import data from a csv file. And I get a structure 
data[[rows]]={first, second,...}.
> Now I want to find the rows in which, say the first entry has a 
specific values.
> By just looking at the data there are for example entries with value 
0.785398.
> But when I try Flatten@Position[data[[All,1]],0.785398] or with 
ToString[0.785398] I just get {}
>
> What's the problem here?
>
> Best,
> Dominic
>
>

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