Create duplicate rows based on conditions in R

问题

I have a data.table that looks like this

dt <- data.table(ID=c("A","A","B","B"),Amount1=c(100,200,300,400),
                 Amount2=c(1500,1500,2400,2400),Dupl=c(1,0,1,0))

   ID Amount1 Amount2 Dupl
1:  A     100    1500    1
2:  A     200    1500    0
3:  B     300    2400    1
4:  B     400    2400    0

I need to duplicate each row that has a 1 in the Dupl column and replace the Amount1 value with the Amount2 value in that duplicated row. Besides that I need to give that duplicated row the value 2 in Dupl. This means it should look like this:

   ID Amount1 Amount2 Dupl
1:  A     100    1500    1
2:  A    1500    1500    2
3:  A     200    1500    0
4:  B     300    2400    1
5:  B    2400    2400    2
6:  B     400    2400    0

Any help is much appreciated! Kind regards,

Tim

回答1:

You could try

rbind(dt,dt[Dupl==1][,c('Amount1', 'Dupl') := list(Amount2, 2)])

回答2:

Using dplyr

require("data.table")
require("dplyr")

#data
dt <- data.table(ID=c("A","A","B","B"),Amount1=c(100,200,300,400),
                 Amount2=c(1500,1500,2400,2400),Dupl=c(1,0,1,0))
#result
rbind(dt,
      dt %>% 
        filter(Dupl==1) %>% 
        mutate(Dupl=2,
               Amount1=Amount2))

#    ID Amount1 Amount2 Dupl
# 1:  A     100    1500    1
# 2:  A     200    1500    0
# 3:  B     300    2400    1
# 4:  B     400    2400    0
# 5:  A    1500    1500    2
# 6:  B    2400    2400    2

回答3:

You can rbind a copy of the sub-setted data with the correct transformations done:

rbind(dt,copy(dt[Dupl==1])[,Amount1:=Amount2][,Dupl:=Dupl+1])
   ID Amount1 Amount2 Dupl
1:  A     100    1500    1
2:  A     200    1500    0
3:  B     300    2400    1
4:  B     400    2400    0
5:  A    1500    1500    2
6:  B    2400    2400    2

Alternatively, you can get the duplicates by sub-setting, and then transform the duplicated rows using an intermediate step. This keeps the duplicated row next to the original as in the example in the question:

x <- dt[rep(seq(dt[,Dupl]),times=dt[,Dupl==1]+1)]
x[duplicated(x),c("Amount1","Dupl"):=list(Amount2,Dupl+1)]
x
   ID Amount1 Amount2 Dupl
1:  A     100    1500    1
2:  A    1500    1500    2
3:  A     200    1500    0
4:  B     300    2400    1
5:  B    2400    2400    2
6:  B     400    2400    0

回答4:

This seems to do what you are asking for. Can probably be refined a bit...

library(splitstackshape)
expandRows(dt, dt$Dupl+1, count.is.col = FALSE)[
  Dupl != 0, Dupl := cumsum(Dupl), by = ID][
    , Amount1 := ifelse(Dupl > 1, Amount2[-1], Amount1)][]
#    ID Amount1 Amount2 Dupl
# 1:  A     100    1500    1
# 2:  A    1500    1500    2
# 3:  A     200    1500    0
# 4:  B     300    2400    1
# 5:  B    2400    2400    2
# 6:  B     400    2400    0

回答5:

Using dplyr's left_join to do the duplication work. Perhaps not elegant, but should be easy to understand.

library(data.table)
library(dplyr)

joiner <- data.frame(Dupl = 1, helper_col= 1:2)

dt <- left_join(dt, joiner) %>%
  mutate(Dupl = ifelse(helper_col == 2 & !is.na(helper_col), 2, Dupl)) %>%
  select(-helper_col) %>%
  mutate(Amount1 = ifelse(Dupl == 2, Amount2, Amount1))

> dt
  ID Amount1 Amount2 Dupl
1  A     100    1500    1
2  A    1500    1500    2
3  A     200    1500    0
4  B     300    2400    1
5  B    2400    2400    2
6  B     400    2400    0

来源：https://stackoverflow.com/questions/28961442/create-duplicate-rows-based-on-conditions-in-r

标签

duplicates

conditional

data.table