Re: How Do You Reduce Multiple Elements in a List?
- To: mathgroup at smc.vnet.net
- Subject: [mg33885] Re: How Do You Reduce Multiple Elements in a List?
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Sun, 21 Apr 2002 06:12:41 -0400 (EDT)
- References: <a9r3ve$ltc$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Bob,
<<Statistics`DataManipulation`
data={1, 1, 1, 1, 1, 2, 2, 2, 4, 4, 4, 4, 4, 4};
Frequencies[data]
{{5,1},{3,2},{6,4}}
Or, own code:
{Length[#],First[#]}&/@Split[Sort[data]]
{{5,1},{3,2},{6,4}}
In this particular case Sort is not needed
{Length[#],First[#]}&/@Split[data]
{{5,1},{3,2},{6,4}}
--
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565
"Bob Harris" <nitlion at mindspring.com> wrote in message
news:a9r3ve$ltc$1 at smc.vnet.net...
> Howdy,
>
> This seems like such a simple thing, yet I've search through the big book
> trying to figure it out. Perhaps someone can help me...
>
> Given a list of integers that generally contains the same number many
times,
> I'd like to reduce it to a list that just gives me the number/count pairs.
> For example, I'd like to convert the list
> {1, 1, 1, 1, 1, 2, 2, 2, 4, 4, 4, 4, 4, 4}
> into
> {{1,5}, {2,3}, (4,6}}
>
> Is there a built-in function to do this? Seems like a histogramming
> operation, but I get no useful matches from ?*Hist*.
>
> Thanks,
> Bob H
>
>