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MathGroup Archive 2005

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Using Select with arrays? (Relative newbie)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54216] Using Select with arrays? (Relative newbie)
  • From: Hugo Mallinson <hfm21 at cam.ac.uk>
  • Date: Sun, 13 Feb 2005 22:17:04 -0500 (EST)
  • Organization: University of Cambridge, England
  • Sender: owner-wri-mathgroup at wolfram.com

The subject might not be entirely correct, but here is my problem:

I have a list of 5-variable data points like

data = {
{1, 1, string1, c, d}
{1, 2, string2, c, d}
{1, 3, string3, c, d}
{1, 4, string4, c, d}
{2, 1, string1, c, d}
{2, 2, string2, c, d}
{3, 1, string3, c, d}
{4, 1, string2, c, d}
{4, 2, string4, c, d}
}


and I want to extract just the points that have 1 (or 2, etc) as their 
first value. I think I should do something like

Select[data, {1, _Integer, _String, _Integer, _Integer}]

but that doesn't work.

Having done that I need to find the maximum value of #2 for each 
string, which I presumably do by the same method as above to extract 
all string1 (or ...2) and then use Map[] and Max[]. I would do this all 
with For loops (revealing my lack of Mathematica chops :-) ) but I'd 
really like to learn how to do this sort of extraction in a 
Mathematica-y way. Any help would be greatly appreciated!

Hugo


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