Groups > comp.soft-sys.math.mathematica > #2881

Re: Mapping to Create Nested Loops

From	Bob Hanlon <hanlonr@cox.net>
Newsgroups	comp.soft-sys.math.mathematica
Subject	Re: Mapping to Create Nested Loops
Date	2011-06-01 11:27 +0000
Organization	Steven M. Christensen and Associates, Inc and MathTensor, Inc.
Message-ID	<is57n9$dgk$1@smc.vnet.net> (permalink)

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GatherBy[myArray, #[[3]] &]

GatherBy[#, #[[3]] &] & /@ myListOfArrays


Bob Hanlon


---- Gregory Lypny <gregory.lypny@videotron.ca> wrote: 

=============
Hello everyone,

I'm trying to learn how to use pure functions and mapping to create what amounts to nested loops. 

Suppose I have a 50 x 6 array called myArray.  The third element of each row is the word red, blue, or green.  If I wanted to break down the array into three according to the value of the third element, I could do this:

Cases[myArray, {__, __, #, __, __, __}] & /@ {red, blue, green}

But what if I needed to do this for more than one array?  Suppose I had three 50 x 6 arrays as

myListOfArrays = {myArray1, myArray2, myArray3} or perhaps the arrays might be imported from files. 


Regards,

Gregory

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Re: Mapping to Create Nested Loops Bob Hanlon <hanlonr@cox.net> - 2011-06-01 11:27 +0000
  Re: Mapping to Create Nested Loops Szabolcs Horvát <szhorvat@gmail.com> - 2011-06-02 11:16 +0000

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