How to find the sum of a column values up to a value in another column in R?

To find the sum of a column values up to a particular value in another column, we can use cumsum function with sum function.

For example, if we have a data frame called df that contains two columns say x and y and we want to find the sum of x values until y is equal to 2 then we can use the following command −

sum(df$x[cumsum(df$y==2)==0])

Example 1

Following snippet creates a sample data frame −

x1<-rpois(20,5) x2<-rpois(20,2) df1<-data.frame(x1,x2) df1

Output

The following dataframe is created −

   x1 x2 1  9  4 2  1  2 3  5  3 4  5  2 5  4  2 6 14  2 7 11  3 8  2  2 9  6  1 10 6  2 11 1  2 12 3  3 13 3  0 14 6  2 15 6  0 16 9  3 17 5  1 18 6  4 19 5  2 20 2  2

To find the sum of x1 until x2 reached 0, add the following code to the above snippet −

x1<-rpois(20,5) x2<-rpois(20,2) df1<-data.frame(x1,x2) sum(df1$x1[cumsum(df1$x2==0)==0])

Output

If you execute all the above given snippets as a single program, it generates the following output −

[1] 67 

Example 2

Following snippet creates a sample data frame −

y1<-round(rnorm(20),1) y2<-round(rnorm(20),1) df2<-data.frame(y1,y2) df2

Output

The following dataframe is created −

    y1    y2 1   2.4  -0.7 2   0.1   2.7 3  -0.7   0.0 4   1.6  -1.9 5   0.2  -1.0 6   0.2   1.7 7   0.7   0.7 8  -0.1  -0.3 9  -0.2  -0.2 10 -1.3   1.4 11 -2.5  -0.4 12  1.2   0.9 13  0.8  -0.4 14  0.8  -1.3 15  0.6   0.5 16 -0.8  -1.8 17  0.4  -0.4 18  0.4   0.6 19 -1.0   0.2 20  0.3   0.6

To find the sum of y1 until y2 reached 0.5, add the following code to the above snippet −

y1<-round(rnorm(20),1) y2<-round(rnorm(20),1) df2<-data.frame(y1,y2) sum(df2$y1[cumsum(df2$y2==0.5)==0])

Output

If you execute all the above given snippets as a single program, it generates the following output −

[1] 3.2