this is my sample data

givendata <- data.table(class = c("a", "b", "c", "d", "e", "f", "g"),  type = c("x", "z", "y", "x", "x", "z", "z"),  risk = c("l", "m", "n", "l", "e", "n", "n"))

And I want to create a column to the right in the data.table givendata by matching the risk column from the data.table givendata to the data.table map and bring the value column.

this is the other data.table.

map<-data.table(fx=c('x','y','z','l','m','n','e','a','b','c','d','e','f','g'),value = runif(14))

I am using this code and it works perfectly.

givendata[map, value2 := i.value, on = .(risk = fx)]

But I need help in making this code a little dynamic.

the risk is a user specified it can be whether class, type or risk.

The way i input it is using the below code:

columnname<-read.xlsx(xlsxFile=//C:/xyz.xlsx ,namedRegion="inputcolname",colNames=FALSE)[,1]

I have tried using the below codes.

givendata[map, value2 := i.value, on = .(get(columnname)= fx)]

givendata[map, value2 := i.value, on = .(givendata[, x ,env = list(x=columnname)]= fx)]