Summing over like elements
- To: mathgroup at smc.vnet.net
- Subject: [mg13855] Summing over like elements
- From: "Mitchell Kaplan" <qmak at pipeline.com>
- Date: Mon, 31 Aug 1998 01:09:16 -0400
- Organization: MindSpring Enterprises
- Sender: owner-wri-mathgroup at wolfram.com
I have a 2 column array. Column 1 has some values, many of which are
repeated. Column 2 has probabilities of these values.
I would like to sum the probabilities for each unique element in column
1. For example:
{{1, .5} , {2, .2} , {1, .1}} should give me:
{{1, .6} , {2, .2}}
I'm sure I can do this with a "Do" loop -- however it seems that in
general "Do's" are pretty innefficient.
Does anyone have any suggestions?
Mitch