[BioC] Average based on group

[Daniel Brewer]

Hi Fabrice,

Check out the library plyr and in particular the function ddply(),
which will do exactly what you want.  There are also various in built
functions to do this kind of thing but the results aren't as sensible as
with ddply.

Dan

**************************************************************

Daniel Brewer

Institute of Cancer Research
Molecular Carcinogenesis
MUCRC
15 Cotswold Road
Sutton, Surrey SM2 5NG
United Kingdom 

Tel: +44 (0) 20 8722 4109
Fax: +44 (0) 20 8722 4141

Email: daniel.brewer at icr.ac.uk 

**************************************************************

>>> Fabrice Tourre <fabrice.ciup at gmail.com> 12/05/2011 16:20 >>>
Dear list,
I have dataframe, the second column is groups factor, each group has
10 items. The data as fellow.
chr10   rs9971029   71916552	0.1
chr10   rs9971029   71916553	0.4
chr10   rs9971029   71916554	0.3
chr10   rs9971029   71916555	0.9
chr10   rs9971029   71916556	1
chr10   rs9971029   71916557	2
chr10   rs9971029   71916558	4
chr10   rs9971029   71916559	0.8	
chr10   rs9971029   71916560	0.9	
chr10   rs9971029   71916561	0.8	
chr10   rs9971030   71916726	0.6	
chr10   rs9971030   71916727	0.5	
chr10   rs9971030   71916728	0.4
chr10   rs9971030   71916729	0.7
chr10   rs9971030   71916730	0
chr10   rs9971030   71916731	0
chr10   rs9971030   71916732	0.6
chr10   rs9971030   71916733	0.8
chr10   rs9971030   71916734	0.9	
chr10   rs9971030   71916735	1

I want to get a average of each item based on the group factor. So at
last I want to get a vector which length is 10.
The value calculated as this:

(0.1+0.6)/2
(0.4+0.5)/2
…
(0.8+1)/2

Thank you very much in advance.

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