R为每个主题添加一个新行

Question

I would like to add one new row for each of the subjects in my dataframe, which looks something like this:

Subject = c("1","5","10")
time = c("2", "2.25", "2.5")
value = c("3", "17", "9")
DF <- data.frame(Subject, time, value)

 Subject time value
1       1    2     3
2       5 2.25    17
3      10  2.5     9

I want to add a new row for each subject with a time = 0 and value = 0, giving this:

Subject = c("1","1","5","5","10","10")
time = c("0","2","0", "2.25","0", "2.5")
value = c("0","3","0", "17","0", "9")
DF2 <- data.frame(Subject, time, value)

 Subject time value
1       1    0     0
2       1    2     3
3       5    0     0
4       5 2.25    17
5      10    0     0
6      10  2.5     9

I have a lot of subjects with a lot of gaps in their subject numbers, and want do this for all of them in a reasonable way. Any suggestions?

Thank you in advance.

Sincerily,

ykl

Answer 1

I would just rbind in the new values (not sure why you specified all your values as character values, here I changed them to numeric)

DF <- data.frame(
   Subject = c(1,5,10), 
   time = c(2, 2.25, 2.5), 
   value = c(3, 17, 9)
)

DF2 <- rbind(
   DF,
   data.frame(Subject = unique(DF$Subject), time="0", value="0")
)

this puts them at the bottom, but you could re-sort of you like

DF2[order(DF2$subject, DF2$time), ]

Answer 2

You can also use interleave from the "gdata" package:

library(gdata)
interleave(DF, data.frame(Subject = 0, time = 0, value = 0))
#     Subject time value
# 1         1 2.00     3
# 11        0 0.00     0
# 2         5 2.25    17
# 1.1       0 0.00     0
# 3        10 2.50     9
# 1.2       0 0.00     0

This uses @MrFlick's sample data.

DF <- data.frame(
  Subject = c(1,5,10), 
  time = c(2, 2.25, 2.5), 
  value = c(3, 17, 9)
)