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Re: Mapping to Create Nested Loops

  • To: mathgroup at smc.vnet.net
  • Subject: [mg119401] Re: Mapping to Create Nested Loops
  • From: Gregory Lypny <gregory.lypny at videotron.ca>
  • Date: Thu, 2 Jun 2011 07:15:02 -0400 (EDT)

Hi Heike,

This is good stuff.  Thank you, Heike.  Either one will do the trick!

Regards,

Gregory


On Wed, Jun 1, 2011, at 5:01 AM, Heike Gramberg wrote:

> Do you want to gather the entries of all the arrays in 3 large lists, or do you want to generate red, blue 
> and green lists for each array separately? In the first case you could try
> 
> Cases[{myArray1, myArray2, myArray3}, {__, __, #, __, __, __}, Infinity] & /@ {red, blue, green}
> 
> which searches all levels of {myArray1,...,myArray3} for the given pattern. In the second case you could 
> do something like
> 
> Function[{lst}, Cases[{lst}, {__, __, #, __, __, __}] & /@ {red, blue, green}] /@ {myArray1, myArray2, myArray3}
> 
> Then %[[1]] would give you the red, blue, green lists for myArray1, etc.
> 
> 
> Heike.
> 
> 
> On 1 Jun 2011, at 09:32, Gregory Lypny 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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