# How to create a column of absolute values in data frames stored in R list?

To create a column of absolute values in data frames stored in R list, we can follow the below steps −

• First of all, create a list of data frames.

• Then, use lapply function to create a column of absolute values in data frames stored in the list.

## Example

#### Create the list of data frames

Using data.frame function to create data frames and list function to create the list of those data frames −

df1<-data.frame(x=sample(-20:10,25))
df2<-data.frame(x=sample(-20:10,25))
List<-list(df1,df2)
List

## Output

On executing, the above script generates the below output(this output will vary on your system due to randomization) −

[[1]]
x
1  -5
2  -19
3  -14
4   1
5   0
6  -3
7  -12
8   9
9   7
10 -13
11 -18
12 -15
13 -10
14 -17
15 -1
16  4
17 -9
18 -11
19 -6
20 -20
21  10
22  8
23 -8
24  3
25 -7

[[2]]
x
1  -7
2  -16
3   10
4  -8
5  -5
6   2
7  -18
8  -6
9  -13
10  5
11 -17
12  9
13 -15
14 -9
15  8
16 -10
17 -2
18 -20
19  6
20 -4
21 -3
22 -1
23 -14
24  7
25  0

Create a column of absolute values

Using lapply function to create a column of absolute values in data frames df1 and df2 stored in the list called List as shown below −

df1<-data.frame(x=sample(-20:10,25))
df2<-data.frame(x=sample(-20:10,25))
List<-list(df1,df2)
lapply(List,function(x) {
+ x$Absolute<-abs(x$x)
+ return(x)
+ })

## Output

[[1]]
x Absolute
1  -6  6
2   3  3
3  -12 12
4  -3  3
5  -9  9
6  -1  1
7  -5  5
8  10 10
9  -4  4
10  4  4
11 -7  7
12  9  9
13 -13 13
14 -8  8
15 -11 11
16 -20 20
17 -16 16
18 -2  2
19 -18 18
20  7 7
21 -17 17
22  1 1
23  0 0
24  8 8
25  6 6
[[2]]
x Absolute
1  -7   7
2  -3   3
3  -5   5
4  -1   1
5  -17 17
6   5   5
7  -13 13
8   0   0
9  -19 19
10 -2   2
11 -6   6
12 -18 18
13  3   3
14 -10 10
15 -9   9
16  6   6
17  7   7
18 -15 15
19 -4   4
20 -16 16
21  2   2
22  9   9
23  4   4
24  1   1
25 -20 20