更简单的选择是 separate_rows

library(tidyr)
separate_rows(dat, ID)
#    ID keep
#1  E87    1
#2  E42    2
#3  E39    3
#4  E16    4
#5  E17    4
#6  E18    4
#7 E760    5
#8 E761    5
#9 E762    5

或者使用OP的方法，在拆分 ID后，用'保持'列，然后堆叠到两列data.frame

Or using the OP's method, after splitting the 'ID', name it with 'keep' column and then stack it to a two column data.frame

stack(setNames(strsplit(dat$ID, ","), dat$keep))