R Merge data.tables with Different Column Names (Example Code)

install.packages("data.table")              # Install data.table package
library("data.table")                       # Load data.table package

install.packages("data.table") # Install data.table package library("data.table") # Load data.table package

dt_A <- data.table(first_ID = 1:5,          # Constructing two data.tables
                   col1 = 1:5)
dt_A
#    first_ID col1
# 1:        1    1
# 2:        2    2
# 3:        3    3
# 4:        4    4
# 5:        5    5

dt_A <- data.table(first_ID = 1:5, # Constructing two data.tables col1 = 1:5) dt_A # first_ID col1 # 1: 1 1 # 2: 2 2 # 3: 3 3 # 4: 4 4 # 5: 5 5

dt_B <- data.table(second_ID = 1:5,
                   col2 = letters[1:5])
dt_B
#    second_ID col2
# 1:         1    a
# 2:         2    b
# 3:         3    c
# 4:         4    d
# 5:         5    e

dt_B <- data.table(second_ID = 1:5, col2 = letters[1:5]) dt_B # second_ID col2 # 1: 1 a # 2: 2 b # 3: 3 c # 4: 4 d # 5: 5 e

dt_merge <- merge.data.table(dt_A, dt_B,    # Applying merge.data.table
                             by.x = "first_ID",
                             by.y = "second_ID")
dt_merge                                    # Show merged data.table in RStudio
#    first_ID col1 col2
# 1:        1    1    a
# 2:        2    2    b
# 3:        3    3    c
# 4:        4    4    d
# 5:        5    5    e

dt_merge <- merge.data.table(dt_A, dt_B, # Applying merge.data.table by.x = "first_ID", by.y = "second_ID") dt_merge # Show merged data.table in RStudio # first_ID col1 col2 # 1: 1 1 a # 2: 2 2 b # 3: 3 3 c # 4: 4 4 d # 5: 5 5 e