CODEWITHSUNDEEP
rdata.table
Hongfei Li
Hongfei Li

Reputation: 59

New columns created in a table emerge in another table using data.table in R

Suppose I have a data table called "dt".

## Generate a data table
library(data.table)
dt = data.table(A=c(1,2,3),B=c(4,5,6))

I want to test some information by creating new columns but I do not want to change the original table, so I create a backup table called "test".

## Create a backup for the original table "dt"
test = dt

However, when I create a new column called "C", I find it also emerges in the original table "dt".

## Create a new column
test[,C:=A+B]
## The new column "C" emerges in the original table "dt"
> colnames(dt)
[1] "A" "B" "C"

This manipulation is likely to be dangerous because it changes the original table. How can I change the test table without changing the original table?

Upvotes: 0

Views: 32

Answers (1)

Ronak Shah
Ronak Shah

Reputation: 389135

Use copy :

library(data.table)
dt = data.table(A=c(1,2,3),B=c(4,5,6))
test <- copy(dt)
test[,C:=A+B]

names(test)
#[1] "A" "B" "C"
names(dt)
#[1] "A" "B"

Upvotes: 1

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