如何将随机或任意列附加到数据帧[R]

Question

Hear me out. Consider an arbitrary case where the new column's elements do not require any information from other columns (which I frustrates base $ and mutate assignment), and not every element in the new column is the same. Here is what I've tried:

df$rand<-rep(sample(1:100,1),nrow(df))
unique(df$rand)
[1] 58

and rest assured, nrow(df)>1 . I think the correct solution might have to do with an apply function?

Answer 1

Your code repeats one single random number nrow(df) times. Try instead:

df$rand<-sample(1:100, nrow(df))

This samples without replacement from 1:100 nrow(df) times. Now this would give you an error if nrow(df)>100 because you would run out of numbers from 1:100 to sample. To make sure you don't get this error, you can instead sample with replacement :

df$rand<-sample(1:100, nrow(df), replace = TRUE)

If, however, you don't want any random numbers to repeat but would also like to prevent the error, you can do something like this:

df$rand<-sample(1:nrow(df), nrow(df))

Answer 2

if I understand this correctly ,I think this is pretty easily doable in dplyr or data.table .

for eg dplyr soln on iris

iris%>%mutate(sample(n()))