使用“AsIs”元素创建一个新的 data.frame

Question

I would like to create a new object with properties similar to the example below.

Although gas is a data frame, it contains "matrix" like columns with "AsIs" type.

As I am a tidyverse user, this structure is strange to me.

data('gas', package = 'gamair')
str(gas)

str(gas)
#'data.frame':  60 obs. of  3 variables:
# $ octane: num  85.3 85.2 88.5 83.4 87.9 ...
# $ NIR   : 'AsIs' num [1:60, 1:401] -0.0502 -0.0442 -0.0469 -0.0467 -0.0509 ...
#  ..- attr(*, "dimnames")=List of 2
#  .. ..$ : chr [1:60] "1" "2" "3" "4" ...
#  .. ..$ : chr [1:401] "900 nm" "902 nm" "904 nm" "906 nm" ...
# $ nm    : num [1:60, 1:401] 900 900 900 900 900 900 900 900 900 900 ...

Answer 1

That "AsIs" means we have to use I() to protect data frame columns. Such protection is a must, if we want to have a matrix or a list, rather than a vector, in a data frame column.

x <- 1:4
Y <- matrix(5:12, nrow = 4, dimnames = list(LETTERS[1:4], letters[1:2]))
Z <- matrix(13:20, nrow = 4)

## wrong
wrong <- data.frame(x = x, Y = Y, Z = Z)
str(wrong)
#'data.frame':  4 obs. of  5 variables:
# $ x  : int  1 2 3 4
# $ Y.a: int  5 6 7 8
# $ Y.b: int  9 10 11 12
# $ Z.1: int  13 14 15 16
# $ Z.2: int  17 18 19 20

## correct
correct <- data.frame(x = x, Y = I(Y), Z = I(Z))
str(correct)
#'data.frame':  4 obs. of  3 variables:
# $ x: int  1 2 3 4
# $ Y: 'AsIs' int [1:4, 1:2] 5 6 7 8 9 10 11 12
#  ..- attr(*, "dimnames")=List of 2
#  .. ..$ : chr [1:4] "A" "B" "C" "D"
#  .. ..$ : chr [1:2] "a" "b"
# $ Z: 'AsIs' int [1:4, 1:2] 13 14 15 16 17 18 19 20