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How to find the sum of rows of a column based on multiple columns in R’s data.table object?
To find the sum of rows of a column based on multiple columns in R’s data.table object, we can follow the below steps−
First of all, create a data.table object.
Then, use aggregate function to find the sum of rows of a column based on multiple columns.
Example
Create the data.table object
Let’s create a data.table object as shown below −
library(data.table)
F1<-sample(c("Male","Female"),25,replace=TRUE)
F2<-sample(c("Low","Medium","High"),25,replace=TRUE)
F3<-sample(c("I","II","III"),25,replace=TRUE)
Response<-sample(1:100,25)
DT<-data.table(F1,F2,F3,Response)
DTOutput
On executing, the above script generates the below output(this output will vary on your system due to randomization) −
F1 F2 F3 Response 1: Male Medium I 2 2: Female Low I 32 3: Female High II 43 4: Male Medium I 24 5: Male Medium III 88 6: Female High I 95 7: Male Low II 68 8: Female High I 74 9: Female High II 12 10: Male High III 42 11: Male High I 62 12: Male High III 67 13: Female High III 38 14: Male Low III 73 15: Female Low III 3 16: Male Medium III 98 17: Female Low I 100 18: Male Medium II 89 19: Female High II 81 20: Female Low I 53 21: Female Medium II 91 22: Female High II 63 23: Female High II 60 24: Male Medium II 72 25: Female Medium III 56 F1 F2 F3 Response
Find the sum of rows of a column based on multiple columns
Using aggregate function to find the sum of rows of column Response based on columns F1, F2, and F3 as shown below −
library(data.table)
F1<-sample(c("Male","Female"),25,replace=TRUE)
F2<-sample(c("Low","Medium","High"),25,replace=TRUE)
F3<-sample(c("I","II","III"),25,replace=TRUE)
Response<-sample(1:100,25)
DT<-data.table(F1,F2,F3,Response)
DT[,sum(Response),by=.(F1,F2,F3)]Output
F1 F2 F3 V1 1: Male Medium I 26 2: Female Low I 185 3: Female High II 259 4: Male Medium III 186 5: Female High I 169 6: Male Low II 68 7: Male High III 109 8: Male High I 62 9: Female High III 38 10: Male Low III 73 11: Female Low III 3 12: Male Medium II 161 13: Female Medium II 91 14: Female Medium III 56
Updated on: 12-Nov-2021
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