[R] Hi , Is it possible select a different number of rows by each group with R????

[arun]

Hi Marta,
It's not clear whether you wanted to select the first "n" rows specified by field2 in the first dataset or just random rows.
##using a modified example if my guess is correct

dat1 <- structure(list(field1 = 1:3, field2 = c(3L, 6L, 4L)), .Names = c("field1", 
"field2"), class = "data.frame", row.names = c(NA, -3L))



dat2 <- structure(list(field1 = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 
3L), field3 = c(0.375, 0.416667, 0.458333, 0.5, 0.541667, 0.583333, 
0.625, 0.666667, 0.708333, 0.75, 0.791667, 0.833333, 0.875, 0.583333, 
0.625, 0.666667, 0.708333, 0.75, 0.791667, 0.833333, 0.875, 0.708333, 
0.75, 0.791667, 0.833333, 0.875), field4 = c("Sp", "Sp", "Sp", 
"Sp", "Sp", "Sp", "Sp", "Sp", "Sp", "Sp", "Sp", "Sp", "Sp", "Sp", 
"Sp", "Sp", "Sp", "Sp", "Sp", "Sp", "Sp", "Sp", "Sp", "Sp", "Sp", 
"Sp"), field5 = c("Rm1", "Rm2", "Rm3", "Rm4", "Rm5", "Rm6", "Jm1", 
"Jm2", "Jm3", "Jm4", "Jm5", "Jm6", "Jm7", "Rm6", "Jm1", "Jm2", 
"Jm3", "Jm4", "Jm5", "Jm6", "Jm7", "Jm3", "Jm4", "Jm5", "Jm6", 
"Jm7")), .Names = c("field1", "field3", "field4", "field5"), class = "data.frame", row.names = c(NA, 
-26L))


##for selecting the first 'n' rows

dat2New <- merge(dat1,dat2,by="field1")
library(plyr)
res1 <- ddply(dat2New,.(field1),function(x) head(x,unique(x$field2)))[,-2]


#or
res2 <- dat2[with(dat1,rep(match(field1, dat2$field1),field2)+sequence(field2)-1),]

A.K.


 Sorry, I think now the message is correct.

Hi , Is it possible select a different number of rows by each group with R????
I must to select different number (specific quantity in field2:Table1) of rows in each group(field1:Table2).
I have these 2 tables:

Table1
field1 field2
1 3
2 6
3 9
4 3
5 3
6 3
7 3
8 9
9 6
10 3
11 3
12 3
13 3
14 3
                       
Table2
field1 field3 field4 field5
1 0.375 Sp Rm1
1 0.416667 Sp Rm2
1 0.458333 Sp Rm3
1 0.5        Sp Rm4
1 0.541667 Sp Rm5
1 0.583333 Sp Rm6
1 0.625 Sp Jm1
1 0.666667 Sp Jm2
1 0.708333 Sp Jm3
1 0.75   Sp Jm4
1 0.791667 Sp Jm5
1 0.833333 Sp Jm6
1 0.875 Sp Jm7

thx!!! 


On Monday, April 21, 2014 4:02 PM, Marta Tobeña <marta_mtm at hotmail.com> wrote:

Hi , Is it possible select a different number of rows by each group with R????
I must to select different number (specific quantity in field2:Table1) of rows in each group(field1:Table2). I have these 2 tables:Table1Table2field1field2field1field3field4field51310.375SpRm12610.416667SpRm23910.458333SpRm34310.5SpRm45310.541667SpRm56310.583333SpRm67310.625SpJm18910.666667SpJm29610.708333SpJm310310.75SpJm411310.791667SpJm512310.833333SpJm613310.875SpJm714320.916667SpJm820.958333SpJm921SpJm1021.041667SpJm1121.083333SpJm1221.125SpJm1321.166667SpJm1421.208333SpJm1521.25SpJm1621.291667SpJm1721.333333SpJm18Thanks youMarta                           
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