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RE: Counting list elements above/below a given value

  • To: mathgroup at smc.vnet.net
  • Subject: [mg17242] RE: [mg17202] Counting list elements above/below a given value
  • From: "Jean-Marie THOMAS" <jmthomas at agat.net>
  • Date: Fri, 30 Apr 1999 02:34:35 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

Try this:
if
mat=Table[Random[],{280},{280}];

then evaluating
Timing at Count[Flatten@mat,_?(#>0.5&)]

I get the following result: (Pentium 150 Mhz)
{10.91 Second,39224}
which sounds quite reasonable to me.

****************************************
Jean-Marie THOMAS
mailto:jmthomas at agat.net
Conseil et Audit en Ingenierie de Calcul
Strasbourg, France
http://www.agat.net
****************************************

-----Original Message-----
From: W.W. Sampson [mailto:w.sampson at umist.ac.uk]
To: mathgroup at smc.vnet.net
Subject: [mg17242] [mg17202] Counting list elements above/below a given value


I wish to count the number of elements within a list above
a given value. I can do this using the following:

Length[Select[Flatten[listname], value > #1&]]

However, my list is a 280 x 280 matrix and consequently
this takes a while to evaluate. My guess is that there
must be something more efficient. I've tried:

Count[listname, value > #1&]

but the output given is 0, which I know to be incorrect.

Any ideas appreciated.

Bill






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