CODEWITHSUNDEEP
rvectordataframe
RNA
RNA

Reputation: 153251

how to get each column as data.frame (instead of a vector) from a data.frame?

Normally when you get a column, it is a vector. How can I keep it as the data.frame with the same row names and corresponding column name?

Upvotes: 11

Views: 3387

Answers (3)

Thraupidae
Thraupidae

Reputation: 675

Instead of calling the desired column with a comma i.e. data.frame[,i] use data.frame[i] to preserve the class as data.frame and also retain row names.

data.frame[,i] #As a vector
data.frame[i] #As a data.frame

Upvotes: 17

Joshua Ulrich
Joshua Ulrich

Reputation: 176648

If you specify a single number when subsetting a data.frame, you get a one-column data.frame. This is different than matrix subsetting, which requires a "missing" i argument to return the entire column (which it then converts to a vector).

# mtcars is a data.frame
mtcars[1]       # first column
str(mtcars[1])  # is still a data.frame
# 'data.frame':   32 obs. of  1 variable:
#  $ mpg: num  21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
# MTCARS is a matrix
MTCARS <- as.matrix(mtcars)
as.matrix(MTCARS)[1]        # only the first element
# [1] 21
str(as.matrix(MTCARS)[,1])  # the first column, as a vector
 Named num [1:32] 21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
 - attr(*, "names")= chr [1:32] "Mazda RX4" "Mazda RX4 Wag" "Datsun 710" ...

Upvotes: 0

Tyler Rinker
Tyler Rinker

Reputation: 109844

use the argument drop = FALSE as in:

mtcars[, 1, drop = FALSE]

Upvotes: 6

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