[R] How to take the ave of two rows in a data frame

[aaront]

Would ?aggregate help?



affy snp wrote:
> 
>> Dear list,
>> I have a data frame like:
>>
>> > log2.ratios[1:3,1:4]
>>            ID                  a1             a2             a3
>> 1 GS1-232B23      -0.0207500 0.17553833  0.21939333
>> 2 RP11-82D16      -0.1896667 0.02645167 -0.03112333
>> 3 RP11-62M23      -0.1761700 0.08214500 -0.04877000
>> 4 RP11-62M23      0.2761700 -0.15214500 -0.05877000
>>
> 
> the 3rd and 4th rows are of the same ID, I would like to take the avarage
> of
> these
> two rows and get the data frame to:
> 
>         ID                  a1             a2             a3
> 1 GS1-232B23      -0.0207500 0.17553833  0.21939333
> 2 RP11-82D16      -0.1896667 0.02645167 -0.03112333
> 3 RP11-62M23      -0.05         -0.035           0.094135
> 
> Can anyone suggest how to deal with this (to take the ave of two rows of
> the
> same ID ) more quickly?
> 
> Thanks a bunch!
> 
> Allen
> 
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> 
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