Creating Character Variables with data.table-CodePudding

Suppose we have the following data.table:

x_dt <- data.table(sexn = c(1,0,0,1,NA,1,NA), country = c("CHN", "JPN", "BGR",  "AUT", " ", "TWN", " "), age=c(35,NA,40,NA,70,18,36))

I am trying to create a variable asia_region, which has a value of 1 when country %chin% c("CHN", "JPN", "KOR", "SGP", "TWN"), a value of 0 when country is not missing and NA when country is missing.

The following code populates 0's when country is missing.

result<-x_dt[ ,asia_region:=ifelse(country %chin% c("CHN", "JPN", "KOR",  "SGP", "TWN"),1,0)]

CodePudding user response：

We can directly coerce the logical to binary with as.integer or , then change the values to NA where the 'country' is blank ("") by specifying a logical condition in i and assignment (:=) for those corresponding elements in 'asia_region' to NA

x_dt[,  asia_region :=  (country %chin% c("CHN", "JPN", "KOR", "SGP", "TWN"))]
x_dt[trimws(country) == "", asia_region := NA_integer_]

-output

> x_dt
   sexn country age asia_region
1:    1     CHN  35           1
2:    0     JPN  NA           1
3:    0     BGR  40           0
4:    1     AUT  NA           0
5:   NA          70          NA
6:    1     TWN  18           1
7:   NA          36          NA

Or if we need a ifelse/fifelse (if/else wouldn't work as it is not vectorized i.e. it expects input expression with length 1 and not more than that)

x_dt[, asia_region := fifelse(trimws(country) == "", NA_integer_,
        fifelse(country %chin% c("CHN", "JPN", "KOR", "SGP", "TWN"), 1, 0))]

CodePudding user response：

How about a dplyr() solution? I'd make a vector of the countries, for easier referencing:

asia_countries <-  c("CHN", "JPN", "KOR",  "SGP", "TWN")

x_dt |>
  dplyr::mutate(asia_region = ifelse(country %in% asia_countries, 1, 0)) |>
  dplyr::mutate(asia_region = ifelse(country == " ", NA, asia_region))