[R] Choosing rows

[ruipbarradas at sapo.pt]

Hello,

First of all, it's better to post data using ?dput. Below, I give an  
example of that  in the lines structure(...).
dat <-
structure(list(rs = c("   rs941873  ", "   rs634552  ", "   rs11107175  ",
"   rs12307687  ", "   rs3917155  ", "   rs1600640  ", "   rs2871865  ",
"   rs2955250  ", "   rs228758  ", "   rs224333  ", "   rs4681725  ",
"   rs7652177  ", "   rs925098  ", "   rs1662837  ", "   rs10071837  "
), n0 = c(81139462, 75282052, 94161719, 47175866, 76444685, 84603034,
99194896, 61959740, 42148205, 34023962, 56692321, 171969077,
17919811, 82168889, 33381581), Pvalue = c(1.52e-07, 0.108, 0.0285,
0.123, 0.68, 0.000275, 0.0709, 0.0317, 0.0772, 0.021, 0.000445,
0.000634, 5.55e-09, 8.66e-05, 0.000574), V1 = c("rs941873", "rs941873",
"rs941873", "rs12307687", "rs941873", "rs12307687", "rs12307687",
"rs12307687", "rs12307687", "rs10071837", "rs10071837", "rs10071837",
"rs925098", "rs925098", "rs925098")), .Names = c("rs", "n0",
"Pvalue", "V1"), row.names = c(NA, -15L), class = "data.frame")

Now, if I understand correctly, the following might do what you want.

tmp <- split(dat[, "Pvalue"], dat[, "V1"])
idx <- unlist(lapply(tmp, function(x) x == min(x)))[order(order(dat[, "V1"]))]
rm(tmp)
result <- dat[idx, ]
result

Hope this helps,

Rui Barradas
 

Citando oslo via R-help <r-help at r-project.org>:

> Hi all;
> I have a big data set (a small part is given below) and V1 column  
> has repeated info in it. That is rs941873, rs12307687... are  
> repeating many times. I need choose only one SNP (in first column  
> named rs) which has the smallest  Pvalue withing V1 column. That is  
> I need choose only one SNP for repeated names in V1 which has the  
> smallest Pvalue.
> Your helps are truly appreciated,Oslo
>
> |  rs  | n0 | Pvalue | V1 |
> |   rs941873  | 81139462 | 1.52E-07 | rs941873 |
> |   rs634552  | 75282052 | 1.08E-01 | rs941873 |
> |   rs11107175  | 94161719 | 2.85E-02 | rs941873  |
> |   rs12307687  | 47175866 | 1.23E-01 | rs12307687 |
> |   rs3917155  | 76444685 | 6.80E-01 | rs941873  |
> |   rs1600640  | 84603034 | 2.75E-04 | rs12307687 |
> |   rs2871865  | 99194896 | 7.09E-02 | rs12307687 |
> |   rs2955250  | 61959740 | 3.17E-02 | rs12307687 |
> |   rs228758  | 42148205 | 7.72E-02 | rs12307687 |
> |   rs224333  | 34023962 | 2.10E-02 | rs10071837 |
> |   rs4681725  | 56692321 | 4.45E-04 | rs10071837 |
> |   rs7652177  | 171969077 | 6.34E-04 | rs10071837 |
> |   rs925098  | 17919811 | 5.55E-09 | rs925098 |
> |   rs1662837  | 82168889 | 8.66E-05 | rs925098  |
> |   rs10071837  | 33381581 | 5.74E-04 | rs925098  |
>
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>
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