Indexing a dataframe with $ inside a function?

Question

Many R textbooks encourage the use of $ to retrieve variables (columns) from data.frames^. However, I found that this does not work inside a function, and I can\'t figure out wh

Answer 1

If you want to perfectly mimic the $ operator you can use [[ and set the parameter exact to FALSE to allow for partial matching.

BOD <- data.frame(demand = 1:10)

myFunc2 <- function(x, y) x[[y, exact = FALSE]]

BOD$dem
## [1]  1  2  3  4  5  6  7  8  9 10

BOD[["dem"]]
## NULL

myFunc2(BOD, "dem")
## [1]  1  2  3  4  5  6  7  8  9 10