Re: A question about pattern-matching
- To: mathgroup at smc.vnet.net
- Subject: [mg63752] Re: [mg63728] A question about pattern-matching
- From: gardyloo <gardyloo at mail.wsu.edu>
- Date: Fri, 13 Jan 2006 04:48:34 -0500 (EST)
- References: <djcgcs$6du$1@smc.vnet.net> <200510230946.FAA10826@smc.vnet.net> <200601120822.DAA10486@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
A big thanks to all who answered my question! (Bob Hanlon, Carl Woll,
Ssezi Mukasa, Peter Pein, ... I hope I didn't leave anyone out) The
solutions proposed (and there were many, as is often the case) all work.
I see now that one of my biggest problems (by no means the only one I
was having) was expecting integers to be considered reals -- they are,
of course, but I was assuming that Mathematica would somehow recognize
things with head Integer to also have head Real. Duh. HOWEVER, my
"testList" was drastically simplified from my original data list, the
components of which in the ordered pairs were ALL Reals (I accidentally
chopped off the decimal places on some of them when preparing the
testList by hand. Mea culpa). I think I'll go back and try the solutions
on the actual data list and see what happens.
Best regards to all,
Curtis O.
gardyloo wrote:
>Hi, all.
>
> I am trying to extract certain parts of a dataset, while retaining
>some of the overall structure. I decided to do it using pattern-matching
>and replacements, but have run into some problems.
>
>First, a small subset of the data:
>
>testList = {{-90, {{60493, 0.061}, {62493, 0.15881}, {64493.5,
>
> 0.559}}}, {-88, {{62493, 0.151}, {64493., 0.61617}, {65993.4,
>
> 0.171}, {68993.10, 0.06}}}, {-86, {{62493.75, 0.14}, {64493.55,
>
> 0.61440}, {65993., 0.18}, {67993, 0.0}, {68993.100, 0.06448}}}};
>
>
>The data consists of lists of the form { integer, { ordered pair1,
>ordered pair2, ... } }, and my goal is to extract the second number in
>each of the ordered pairs, while retaining the lists' overall structure.
>So, for example, from testList, I'd want something like
> { { 0.061, 0.15881, 0.559}, {0.151, 0.61617, 0.171, 0.06}, {0.14,
>0.61440, 0.18, 0.0, 0.06448}}
>returned.
>
>I've tried several patterns, with variously named bits, and only some of
>them make sense to me (and none of them, yet, return what I really
>want). Can someone explain them to me?
>
>I'd expect this one to return the list of lists of ordered pairs. It
>returns the full testList:
>
>testList /. {{(z_)?NumberQ, x:{{_Real, _Real}...}} -> x}
>
>
>On the other hand, this one returns only the lists of ordered pairs:
>
>testList /. {{(z_)?NumberQ, x:{{_, _}...}} -> x}
>
>I thought that one was free to "type" the parts of the pattern to
>return. I also thought that naming the parts rather freely was allowed.
>The first three of the following return what I would expect, but the
>last one, in naming the first of the ordered pairs' elements, returns
>the testList apparently unchanged:
>
>In[54]:=
>
>testList /. {{z_, {x:{_, _}...}} -> z}
>
>testList /. {{z_, {x:{_, _}...}} -> x}
>
>testList /. {{z_, x:{{_, _}...}} -> x}
>
>testList /. {{z_, {x:{a_, _}...}} -> x}
>
>Out[54]=
>
>{-90, -88, -86}
>
>Out[55]=
>
>{{60493, 0.061}, {62493, 0.15881}, {64493.5, 0.559}, {62493, 0.151}, {64493., 0.61617},
>
> {65993.4, 0.171}, {68993.1, 0.06}, {62493.75, 0.14}, {64493.55, 0.6144}, {65993., 0.18},
>
> {67993, 0.}, {68993.1, 0.06448}}
>
>Out[56]=
>
>{{{60493, 0.061}, {62493, 0.15881}, {64493.5, 0.559}}, {{62493, 0.151}, {64493., 0.61617},
>
> {65993.4, 0.171}, {68993.1, 0.06}}, {{62493.75, 0.14}, {64493.55, 0.6144}, {65993., 0.18},
>
> {67993, 0.}, {68993.1, 0.06448}}}
>
>Out[57]=
>
>{{-90, {{60493, 0.061}, {62493, 0.15881}, {64493.5, 0.559}}},
>
> {-88, {{62493, 0.151}, {64493., 0.61617}, {65993.4, 0.171}, {68993.1, 0.06}}},
>
> {-86, {{62493.75, 0.14}, {64493.55, 0.6144}, {65993., 0.18}, {67993, 0.},
>
> {68993.1, 0.06448}}}}
>
>
> Although a solution would help me a lot, I really would like to know
>what I'm missing in applying these replacement rules.
>
> Thanks!
> Curtis O.
>
>
>
>
- References:
- A question about pattern-matching
- From: gardyloo <gardyloo@mail.wsu.edu>
- A question about pattern-matching