Re: Using Select with arrays? (Relative newbie)

• To: mathgroup at smc.vnet.net
• Subject: [mg54258] Re: Using Select with arrays? (Relative newbie)
• From: János <janos.lobb at yale.edu>
• Date: Mon, 14 Feb 2005 21:50:53 -0500 (EST)
• References: <200502140317.WAA14058@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Well, I did not read to the end at first.
If you want to use Select to select the element which has maximum in
its #2 location from all those who have 1 in their #1 location, then
you can do something like:

In[23]:=
Select[Select[data,
#1[[1]] == 1 & ],
#1[[2]] == Max[
Select[data,
#1[[1]] == 1 & ][[All,
2]]] & ]
Out[23]=
{{1, 4, string4, c, d}}

János

On Feb 13, 2005, at 10:17 PM, Hugo Mallinson wrote:

> 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

----------------------------------------------
Trying to argue with a politician is like lifting up the head of a
corpse.
(S. Lem: His Master Voice)

```

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