[R] Mean of matched data

robgriffin247 rg.rforum at hotmail.co.uk
Wed Jul 18 11:54:13 CEST 2012

I think/hope there will be a simple solution to this but google-ing has
provided no answers (probably not using the right words)

I have a long data frame of >2 000 000 rows, and 6 columns. Across this
there are 24 000 combinations of gene in a column (n=12000) and gender in a
column (n=2... obviously). I want to create 2 new columns in the data frame
that on each row gives, in one column the mean value (of gene expression, in
the column called "value") for that row's gene&gender combination, and in
the other column the standard deviation for the gene&gender combination.

Any suggestions?


Example of the top of the data frame:

gene	variable	value	gender	line	rep
1	CG10000	X208.F1.30456	4.758010	Female	208	1
2	CG10000	X365.F2.30478	4.915395	Female	365	2
3	CG10000	X799.F2.30509	4.641636	Female	799	2
4	CG10000	X306.M2.32650	4.550676	Male	306	2
5	CG10000	X712.M2.30830	4.633811	Male	712	2
6	CG10000	X732.M2.30504	4.857564	Male	732	2
7	CG10000	X707.F1.31120	5.104165	Female	707	1
8	CG10000	X514.F2.30493	4.730814	Female	514	2

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