Select Value from Previous Row of data.table in R (Example Code)

In this tutorial you’ll learn how to select values from the previous row of a data.table in the R programming language.

Setting up the Example

install.packages("data.table")     # Install data.table package
library("data.table")              # Load data.table
my_dt <- data.table(x = 10:15,     # Construct data.table in R
                   y = 1:6)
my_dt                              # Print data.table in RStudio console
#     x y
# 1: 10 1
# 2: 11 2
# 3: 12 3
# 4: 13 4
# 5: 14 5
# 6: 15 6

Example: Use Previous Row of data.table for Calculation

my_dt_new <- my_dt                 # Duplicate data.table
my_dt_new[ , z := x + shift(y)]    # Add columns using shift()
my_dt_new                          # Show new data.table in RStudio console
#     x y  z
# 1: 10 1 NA
# 2: 11 2 12
# 3: 12 3 14
# 4: 13 4 16
# 5: 14 5 18
# 6: 15 6 20

Related Articles

Please find some related R programming language tutorials on topics such as RStudio, extracting data, and groups in the following list:

Leave a Reply

Your email address will not be published.

Fill out this field
Fill out this field
Please enter a valid email address.
You need to agree with the terms to proceed

Menu
Top