numbering by groups [duplicate]

Answer 1

Using dplyr

dat <- data.frame(ID = rep(1:3, c(2, 3, 5)), val = rnorm(10))

library(dplyr)
dat %>% group_by(ID) %>%
    mutate(number.in.group = 1:n())

Answer 2

There are probably better ways but one could use tapply on the IDs and toss in a function that returns a sequence.

# Example data
dat <- data.frame(ID = rep(1:3, c(2, 3, 5)), val = rnorm(10))

# Using tapply with a function that returns a sequence
dat$number.in.group <- unlist(tapply(dat$ID, dat$ID, function(x){seq(length(x))}))
dat

which results in

> dat
   ID          val number.in.group
1   1 -0.454652118               1
2   1 -2.391824247               2
3   2  0.530832021               1
4   2 -1.671043812               2
5   2 -0.045261549               3
6   3  2.311162484               1
7   3 -0.525635803               2
8   3  0.008588811               3
9   3  0.078942033               4
10  3  0.324156111               5

Answer 3

Here's another solution

require(plyr)
ddply(dat, .(ID), transform, num_in_grp = seq_along(hit))

Answer 4

You could just use rle and sequence:

dat <- read.table(text = "ID  Shoot  hit
+ 1     10    2
+ 1      9    3
+ 1      8    1
+ 2     10    8
+ 2      8    8
+ 2     11   10
+ 2      7    2
+ 3      9    2
+ 4      6    6
+ 4      6    5",sep = "",header = TRUE)

> sequence(rle(dat$ID)$lengths)
 [1] 1 2 3 1 2 3 4 1 1 2

Indeed, I think sequence is intended for exactly this purpose.

Answer 5

df$number.in.group <- unlist(lapply(as.vector(unlist(rle(df$ID)[1])), function(x) 1:x))

Answer 6

I compared your anwsers and IShouldBuyABoat is the most promissing. I found that function ave could be applied even if dataset is not sorted according to the grouping variable.

Let consider dataset:

dane<-data.frame(g1=c(-1,-2,-2,-2,-3,-3,-3,-3,-3),
             g2=c('reg','pl','reg','woj','woj','reg','woj','woj','woj'))

Joran anwser and applied to my example:

> sequence(rle(as.character(dane$g2))$lengths)
[1] 1 1 1 1 2 1 1 2 3

Simon Urbanek proposition and results:

> unlist(lapply(table(dane$g2),seq.int))
  pl reg1 reg2 reg3 woj1 woj2 woj3 woj4 woj5 
   1    1    2    3    1    2    3    4    5 

IShouldBuyABoat code gives correct anwser:

> as.numeric(ave(as.character(dane$g1),as.character(dane$g1),FUN=seq_along))
[1] 1 1 2 3 1 2 3 4 5