How to find the sum of numerical columns based on the combination of values in
categorical columns in R data frame?

To find the sum of numerical columns based on the combination of values in categorical columns in R data frame, we can follow the below steps −

• First of all, create a data frame.
• Then, find the sum of numerical columns based on the combination of values in categorical columns by using recast function of reshape2 package with sum function.

Create the data frame

Example

Let's create a data frame as shown below −

 Live Demo

> x1<-rpois(20,2)
> x2<-rpois(20,5)
> x3<-rpois(20,1)
> x4<-rpois(20,10)
> f1<-sample(LETTERS[1:3],20,replace=TRUE)
> f2<-sample(letters[1:3],20,replace=TRUE)
> df<-data.frame(x1,x2,x3,x4,f1,f2)
> df

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

Output

  x1 x2 x3 x4 f1 f2
1  1  6  0 11  B  c
2  2  3  3 16  B  a
3  4  2  0 13  B  b
4  1  3  0  4  B  c
5  0  4  0 10  A  b
6  1  8  3  8  C  c
7  2  4  0  2  A  c
8  0  1  1 12  A  b
9  3  4  0 15  B  b
10 0  1  1  4  A  a
11 2  8  0  6  C  b
12 1  4  1 13  C  c
13 1  4  1 13  A  b
14 2  6  2 11  A  b
15 3  5  0 10  A  a
16 1  4  0 17  A  c
17 2  4  1  4  B  a
18 1  4  0 11  B  b
19 3  3  1  8  B  c
20 4  6  3  5  A  a

Find the sum of numerical columns based on the combination of values in categorical columns

Example

Using recast function to find the sum of columns x1, x2, x3, and x4 based on f1 and f2 in df −

 Live Demo

> x1<-rpois(20,2)
> x2<-rpois(20,5)
> x3<-rpois(20,1)
> x4<-rpois(20,10)
> f1<-sample(LETTERS[1:3],20,replace=TRUE)
> f2<-sample(letters[1:3],20,replace=TRUE)
> df<-data.frame(x1,x2,x3,x4,f1,f2)
> library(reshape2)
> recast(df,variable~f1+f2,sum)

Output

Using f1, f2 as id variables
  variable A_a A_b A_c B_a B_b B_c C_b C_c
1  x1  7  3  3  4  8  5 2  2
2  x2 12 15  8  7 10 12 8 12
3  x3  4  4  0  4  0  1 0  4
4  x4 19 46 19 20 39 23 6 21