How to divide the row values by row sum in data.table object in R?


To divide the row values by row sum in R’s data.table object, we can follow the below steps −

  • First of all, create a data.table object.
  • Then, use apply function to divide the data.table object row values by row sum.

Create the data.table object

Let’s create a data.table object as shown below −

library(data.table)
x<-rpois(25,2)
y<-rpois(25,2)
DT<-data.table(x,y)
DT

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

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

Divide the data.table object row values by row sum

Using apply function to divide the row values of DT by row sum −

library(data.table)
x<-rpois(25,2)
y<-rpois(25,2)
DT<-data.table(x,y)
DT_new<-t(apply(DT,1, function(x) x/sum(x)))
DT_new

Output

         x          y
[1,] 0.5714286 0.4285714
[2,] 0.0000000 1.0000000
[3,] 0.3333333 0.6666667
[4,] 0.5000000 0.5000000
[5,] 1.0000000 0.0000000
[6,] 0.4000000 0.6000000
[7,] 0.0000000 1.0000000
[8,] 0.3333333 0.6666667
[9,] 1.0000000 0.0000000
[10,] 0.3333333 0.6666667
[11,] 0.2000000 0.8000000
[12,] 0.2000000 0.8000000
[13,] 0.8000000 0.2000000
[14,] 0.2500000 0.7500000
[15,] 0.3333333 0.6666667
[16,] 0.2500000 0.7500000
[17,] 0.5000000 0.5000000
[18,] 0.0000000 1.0000000
[19,] 0.0000000 1.0000000
[20,] 0.3333333 0.6666667
[21,] 0.5000000 0.5000000
[22,] 1.0000000 0.0000000
[23,] 0.6666667 0.3333333
[24,] 0.5000000 0.5000000
[25,] 0.5000000 0.5000000

Updated on: 13-Aug-2021

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