[BioC] Average based on group

[Fabrice Tourre]

Thanks for your reply. But it cannot be for my purpose. In fact, there
are two snps in the example, rs9971029 and rs9971030.

I expect fellow output with the fellow data:

0.35 0.45 0.35 0.80 0.50 1.00 2.30 0.80 0.90 0.90

You can run this example to get above value

-----------------------------R code------------------------------------
df<-structure(list(seqnames = structure(c(1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label =
"chr10", class = "factor"),
    snp.id = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
    1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("rs9971029",
    "rs9971030"), class = "factor"), position = c(71916552L,
    71916553L, 71916554L, 71916555L, 71916556L, 71916557L, 71916558L,
    71916559L, 71916560L, 71916561L, 71916726L, 71916727L, 71916728L,
    71916729L, 71916730L, 71916731L, 71916732L, 71916733L, 71916734L,
    71916735L), score = c(0.1, 0.4, 0.3, 0.9, 1, 2, 4, 0.8, 0.9,
    0.8, 0.6, 0.5, 0.4, 0.7, 0, 0, 0.6, 0.8, 0.9, 1)), .Names = c("seqnames",
"snp.id", "position", "score"), class = "data.frame", row.names = c(NA,
-20L))

a<-df[1:10,]
b<-df[11:20,]
cbind(a,b)->c
(c[,4]+c[,8])/2
----------------------------------------------------------------

The data is :

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