How can I add a column from one dataframe to another with certain conditions? [duplicate]

Question

I have 2 dataframes and I am using R:

Van	Route	Time
U31	23452	8:00
U72	13422	7:00
U98	53622	8:00
U24	16622	8:00
U75	76422	6:00
U45	98422	8:00
U27	46422	9:00

Van	Seats
U27	20
U72	22
U24	13
U98	16
U75	22
U45	12
U31	22

the problem here is that both data frames are ordered differently and I would like to add the column of "Seats" to my first DF.

This is the result I want:

Van	Route	Time	Seats
U31	23452	8:00	22
U72	13422	7:00	22
U98	53622	8:00	16
U24	16622	8:00	13
U75	76422	6:00	22
U45	98422	8:00	12
U27	46422	9:00	20

So I would like to basically add this column with the condition that DF1$Vans = DF2$Vans!!!

Thanks in advance :))

Answer 1

# set as data.table
lapply(list(df1, df2), \(i) setDT(i))

# join
df2[df1
    , on=.(Vans)
    , mget(c("i.Van", "x.Seats"))
    ]
# assuming df1 has columns "Van", Route", "Time" as OP has not specified

Answer 2

Perform a simple merge:

newdf = merge(df1, df2, by="Van")

If df2 includes more columns, subset df2 to the desired column and column used to merge:

newdf = merge(df1, df2[,c("Van","Seats")], by="Van")

Answer 3

You can do this:

library(dplyr)
left_join(df1, df2[,c("Van","Seats")], by = "Van")

df2[,c("Van","Seats")] subsets df2 on two columns: Van, which is the column df1 and df2have in common and based on which the join can be performed, as well as Seats, the column you want to add to df1