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MathGroup Archive 2005

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Re: Count using pattern on two different matrices

  • To: mathgroup at smc.vnet.net
  • Subject: [mg57088] Re: [mg57079] Count using pattern on two different matrices
  • From: "David Park" <djmp at earthlink.net>
  • Date: Sun, 15 May 2005 03:03:42 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Lee,

First, generating a test case...

genrandombool := If[Random[Integer, {0, 1}] == 0, False, True]

L1 = Table[genrandombool, {3}, {2}]
L2 = Table[genrandombool, {3}, {3}]
{{True, False}, {False, True}, {True, False}}
{{True, False, True}, {False, True, True}, {False, False, True}}

Plus @@ MapThread[If[! Part[#1, 2] && Part[#2, 3], 1, 0] &, {L1, L2}]
2

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/ 


From: Lee Newman [mailto:leenewm at umich.edu]
To: mathgroup at smc.vnet.net

I have two matrices with an equal number of rows, but not necessarily 
columns, for example:

L1= {{True,False},{False, True},{False, False}, etc.....} ;
L2= {{True,False,False},{True, True,True},{False, True,False}, etc.....} ;

I would like to compute a count of the number of rows in which one of 
the columns of L1 meets some criterion, and one of the columns of L2 
meets some criterion, i.e.  If L1[[row,2 ]]==False  and 
L2[[row,3]]==True  then this row contributes 1 to the count.

I suspect that there is an elegant way to do this, perhaps using Count[] 
and MapThread, but I can't figure it out other than resorting to a 
rather clumsy For or Do loop that would check line by line and maintain 
a counter.

Any help would be appreciated,
Lee





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