Merging two columns into one in R

Question

I have the following data frame, and am trying to merge the two columns into one, while replacing NA\'s with the numeric values.

ID    A     B
1         


        

Answer 1

Assuming either A or B have a NA, that would work just fine:

# creating initial data frame (actually data.table in this case)
library(data.table)
x<- as.data.table(list(ID = c(1,2,3,4), A = c(3, NA, NA, 1), B = c(NA, 2, 4, NA)))
x
#   ID  A  B
#1:  1  3 NA
#2:  2 NA  2
#3:  3 NA  4
#4:  4  1 NA


#solution
y[,New := na.omit(c(A,B)), by = ID][,c("A","B"):=NULL]
y
#   ID New
#1:  1   3
#2:  2   2
#3:  3   4
#4:  4   1