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How to find the sum of values based on key in other column of an R data frame?
If we have a column that is key that means we want to use that column as an independent variable and find the statistical values such as sum, mean, standard deviation, range, etc. for the dependent variable. This can be done with the combination of with and tapply function as shown in the below examples.
Consider the below data frame −
Example
x1<-sample(c("A","B","C"),20,replace=TRUE)
y1<-rpois(20,5)
df1<-data.frame(x1,y1)
df1Output
x1 y1 1 C 0 2 A 4 3 C 5 4 C 5 5 A 5 6 C 3 7 B 7 8 B 6 9 C 6 10 C 13 11 C 6 12 C 5 13 C 6 14 A 7 15 B 4 16 C 1 17 C 7 18 B 6 19 B 3 20 B 5
Finding the sum of y1 for values in x1 −
with(df1,tapply(y1,x1,FUN=sum))
A B C 16 31 57
Example
x2<-sample(c("India","Indonesia","UK"),20,replace=TRUE)
y2<-rpois(20,10)
df2<-data.frame(x2,y2)
df2Output
x2 y2 1 India 11 2 India 8 3 Indonesia 16 4 India 8 5 Indonesia 10 6 UK 16 7 India 16 8 Indonesia 9 9 Indonesia 11 10 India 9 11 UK 7 12 India 14 13 Indonesia 9 14 India 12 15 UK 8 16 Indonesia 10 17 UK 14 18 India 9 19 India 13 20 Indonesia 10
Finding the sum of y2 for values in x2 −
with(df2,tapply(y2,x2,FUN=sum))
India Indonesia UK 100 75 45
Updated on: 06-Feb-2021
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