R – how to drop columns by passing variable name with dplyr

dplyrr

I have a df as follows:

a <- data_frame(keep=c("hello", "world"),drop = c("nice", "work"))
a
Source: local data frame [2 x 2]
   keep  drop
  (chr) (chr)
1 hello  nice
2 world  work

I can use a %>% select(-drop) to drop the column without problem. however, if I want to pass a variable to present drop column, then it returns error.

name <- "drop"
a  %>% select(-(name))

Error in -(name) : invalid argument to unary operator

Best Answer

You can use one_of to find the column positions and then use - to drop it, select(-one_of(name)), if you check ?select, the usage is documented in the Drop variable section in the Examples:

name <- "drop"
a %>% select(-one_of(name))

# A tibble: 2 × 1
#   keep
#  <chr>
#1 hello
#2 world

Or with select_, you need to paste - with the column names to drop them and pass the pasted column names to the .dots parameter if there are more than one column to be dropped:

name <- "drop"
a %>% select_(.dots = paste("-", name))

# A tibble: 2 × 1
#   keep
#  <chr>
#1 hello
#2 world

Related Solutions

R – Drop data frame columns by name

You can use a simple list of names :

DF <- data.frame(
  x=1:10,
  y=10:1,
  z=rep(5,10),
  a=11:20
)
drops <- c("x","z")
DF[ , !(names(DF) %in% drops)]

Or, alternatively, you can make a list of those to keep and refer to them by name :

keeps <- c("y", "a")
DF[keeps]

EDIT : For those still not acquainted with the drop argument of the indexing function, if you want to keep one column as a data frame, you do:

keeps <- "y"
DF[ , keeps, drop = FALSE]

drop=TRUE (or not mentioning it) will drop unnecessary dimensions, and hence return a vector with the values of column y.

R – How to drop columns by name in a data frame

You should use either indexing or the subset function. For example :

R> df <- data.frame(x=1:5, y=2:6, z=3:7, u=4:8)
R> df
  x y z u
1 1 2 3 4
2 2 3 4 5
3 3 4 5 6
4 4 5 6 7
5 5 6 7 8

Then you can use the which function and the - operator in column indexation :

R> df[ , -which(names(df) %in% c("z","u"))]
  x y
1 1 2
2 2 3
3 3 4
4 4 5
5 5 6

Or, much simpler, use the select argument of the subset function : you can then use the - operator directly on a vector of column names, and you can even omit the quotes around the names !

R> subset(df, select=-c(z,u))
  x y
1 1 2
2 2 3
3 3 4
4 4 5
5 5 6

Note that you can also select the columns you want instead of dropping the others :

R> df[ , c("x","y")]
  x y
1 1 2
2 2 3
3 3 4
4 4 5
5 5 6

R> subset(df, select=c(x,y))
  x y
1 1 2
2 2 3
3 3 4
4 4 5
5 5 6

Best Answer

Related Solutions

R – Drop data frame columns by name

R – How to drop columns by name in a data frame

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