       Re: Problem with Position

• To: mathgroup at smc.vnet.net
• Subject: [mg119650] Re: Problem with Position
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Thu, 16 Jun 2011 04:00:21 -0400 (EDT)

```Perhaps the numbers have more decimal places than what is displayed and you
need to round to the precision of the index key.

choices = {0.123456, 0.654321, 0.785398};

data = Table[{
RandomChoice[choices] + 10^-7*Random[],
RandomReal[], RandomReal[]}, {10}];

Flatten@
Position[N[Round[data[[All, 1]], 10^-6]],
0.785398]

{2, 5, 6, 9}

Flatten@
Position[N[Round[data[[All, 1]], 10^-6]], #] & /@
choices

{{1, 3, 4, 8}, {7, 10}, {2, 5, 6, 9}}

Alternatively,

Flatten@
Position[data[[All, 1]],
_?(Abs[# - 0.785398] < 10^-6 &)]

{2, 5, 6, 9}

Table[
Flatten@Position[data[[All, 1]],
_?(Abs[# - c] < 10^-6 &)],
{c, choices}]

{{1, 3, 4, 8}, {7, 10}, {2, 5, 6, 9}}

Bob Hanlon

---- "Dominic W=C3=B6rner" <dominic.woerner at 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

```

• Prev by Date: Re: Diferent colors for two surfaces, problem with PLOTSTYLE
• Next by Date: Interval and IntervalIntersection with a List
• Previous by thread: Re: Problem with Position
• Next by thread: Re: Problem with Position