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How to change the sign of even number rows in column of a data.table object in R?
To change the sign of even number rows in a data.table object in R, we can follow the below steps −
First of all, create a data.table object.
Then, use vector multiplication with 1 and minus 1 to change the sign of even number rows.
Example
Create the data.table object
Let’s create a data.table object as shown below −
library(data.table) x<-sample(-5:5,30,replace=TRUE) DT<-data.table(x) DT
Output
On executing, the above script generates the below output(this output will vary on your system due to randomization) −
x
1: 2
2: 3
3: 5
4: 2
5: 5
6: -5
7: 2
8: 3
9: 0
10: 3
11: 3
12: -3
13: -1
14: -4
15: 5
16: 5
17: -1
18: -4
19: -5
20: -1
21: 4
22: 5
23: 2
24: 0
25: -3
26: 0
27: -2
28: 1
29: 4
30: -1
xChange the sign of even number rows
Using vector multiplication with 1 and minus 1 to change the sign of even number rows in column x of data.table object DT −
library(data.table) x<-sample(-5:5,30,replace=TRUE) DT<-data.table(x) DT$x<-DT$x*c(1,-1) DT
Output
x
1: 2
2: -3
3: 5
4: -2
5: 5
6: 5
7: 2
8: -3
9: 0
10: -3
11: 3
12: 3
13: -1
14: 4
15: 5
16: -5
17: -1
18: 4
19: -5
20: 1
21: 4
22: -5
23: 2
24: 0
25: -3
26: 0
27: -2
28: -1
29: 4
30: 1
x
Updated on: 09-Nov-2021
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