I want to drop a column from a data.frame. But when I do, an attribute of the data.frame is lost, which I don't want. First the setup:
d <- data.frame(a = 1, b = 2, c = 3)
attr(d, "test_attribute") <- "something"
d2 <- d
d
#> a b c
#> 1 1 2 3
The test attribute is present:
attributes(d2) # contains $test_attribute [1] "something"
Now I want to remove the second column - but most ways destroy that attribute:
attributes(d2[, -2]) # it's gone
attributes(dplyr::select(d2, -2)) # it's gone
I found one way to preserve it:
d3 <- d2
d3[2] <- NULL
attributes(d3)
Why does the test_attribute get dropped in the first two cases, but not when using this last method?