Make a new column based on conditions, data.table R-CodePudding

I have a function that contains a data.table with specific values:

 add_q <- function () {

DT = data.table (X = c("A", "A1", "B", "B1"), Y = c("C", "C1", "D", "D1"))}

This will give my two columns X and Y with the values. I want to make a 3rd column that would have the values YES for values that have A, C, A1, C1 and the value NO for the rest.

How to do that?

CodePudding user response：

Updated shortened code (many thanks to @B. Christian Kamgang:

Using fifelse we could do something like this:

library(data.table)

add_q <- function (DT, Z) {

  setDT(DT)[, Z :=  fifelse(grepl("A|C", X) | grepl("A|C", Y), "Yes", "NO")]
  DT
  }

DT = data.table (X = c("A", "A1", "B", "B1"), Y = c("C", "C1", "D", "D1"))

add_q(DT, Z)
DT

    X  Y   Z
1:  A  C YES
2: A1 C1 YES
3:  B  D  NO
4: B1 D1  NO

CodePudding user response：

We can try grepl like below

DT[
  ,
  Z := fifelse(
    Reduce(`&`, lapply(.SD, grepl, pattern = "^(A|C)")), 
    "YES", 
    "NO"
  )
]

which gives

> DT
    X  Y   Z
1:  A  C YES
2: A1 C1 YES
3:  B  D  NO
4: B1 D1  NO