I want to figure out how many unique NR have all C_P values NA.
DT <- structure(list(NR = c(10001111, 10001111, 10001113, 10001114,
10001115), C_P = c("8851", "NA", "8873", "NA", "NA"
), B_LAND = c("NL", "NL", "NL", "NL", "NL")), row.names = c(NA,
-5L), class = c("data.table", "data.frame"))
NR C_P B_LAND
1: 10001111 8851 NL
2: 10001111 NA NL
3: 10001113 8873 NL
4: 10001114 NA NL
5: 10001115 NA NL
I am struggling to get the syntax right. I attempted;
DT[, .(uniqueNR_without_C_P = uniqueN(is.na(C_P)), by = NR]
The desired output is 2, since there are two unique NR, for which there is no C_P.
>Solution :
Usually you could do:
DT[, all(is.na(C_P)), NR][, sum(V1)]
But since there no NA value in your data but the characther "NA" you can do smth like:
is_string.NA = function(x) x == "NA"
DT[, all(is_string.NA(C_P)), NR][, sum(V1)]
Alternatively:
uniqueN(DT$NR) - uniqueN(DT[!is_string.NA(C_P)]$NR)