matching by date and category (2 way match)-CodePudding

I have a couple of large dataframes of the following pattern(s), df1:

        date cat value code
2022-07-10    A   0.6  12Az
2022-07-10    B   0.5  131x
2022-07-12    C   0.5  55tg
2022-07-18    A   0.1  fs12
2022-07-19    C   0.6  55tg
2022-07-19    B   0.6  zz12

df2:

       date cat allocation code
2022-07-10    A   100  12Az
2022-07-10    B   450  131x
2022-07-12    C   220  55tg
2022-07-18    A   360  fs12
2022-07-19    C   221  55tg
2022-07-19    B   485  zz12

What I'd like to do is bring the 'allocation' column from df2 into df1 using something like a match function that matches the data from the 'date' and 'cat' columns.

I was hoping it would be as easy as writing something like:

df1$allocation <- df2$allocation[match(df1$date, df2$date & df1$cat, df2$cat)]

But unfortunately that just throws up errors for me. Does anyone have any advice on how to fix this?

CodePudding user response：

Sounds like a job for the dplyr::left_join() function. It would be similar to

library(dplyr)
left_join(df1, df2, by=c("date"="date", "cat"="cat"))