Question

How can I drop columns by name in a data frame

Answer 1

We can Drop Columns by name in a Data frame using following two methods:

Create a data frame

The following code creates a sample data frame which we will use for demonstration.
set.seed(556)
mydata <- data.frame(m=letters[1:5], x=runif(5,10,50), y=sample(5), z=rnorm(5))
# Delete column by name

Method I :

One of the most easiest way to drop columns is by using subset() function.
The following code tells R to drop variables x and z.
The '-' sign indicates dropping variables.
Note: Don't specify the variable names in quotes when using subset() function.

df = subset(mydata, select = -c(x,z) )

> mydata
  m        x y           z
1 a 33.83910 2 -1.02569136
2 b 23.50851 3  0.59367584
3 c 22.91966 1 -0.06436851
4 d 33.18065 4 -0.04719129
5 e 13.79128 5 -1.80186137

> df
  m y
1 a 2
2 b 3
3 c 1
4 d 4
5 e 5

Method II :

The function names() returns all the column names and the '!' sign indicates negation.
drop <- c("x","z") #we are creating a character vector named drop in which we are storing column names x and z
df = mydata[,!(names(mydata) %in% drop)] #Selecting all the variables except the column names specified in the vector drop. The '!' sign indicates negation.
> df
  m y
1 a 2
2 b 3
3 c 1
4 d 4
5 e 5

It can also be written like :  df = mydata[,!(names(mydata) %in% c("x","z"))]

> set.seed(556)
> mydata <- data.frame(m=letters[1:5], x=runif(5,10,50), y=sample(5), z=rnorm(5))
> df = mydata[,!(names(mydata) %in% c("x","z"))]
> df
  m y
1 a 2
2 b 3
3 c 1
4 d 4
5 e 5

Answer 2

Hi,

The most easiest way to drop columns is by using subset() function. In the code below, we are telling R to drop variables x and z. The '-' sign indicates dropping variables.

$ mydata <- data.frame(a=letters[1:5], x=runif(5,10,50), y=sample(5), z=rnorm(5))
$ df = subset(mydata, select = -c(x,z) )