Simple lookup to insert values in an R data frame

Question

This is a seemingly simple R question, but I don't see an exact answer here. I have a data frame (alldata) that looks like this:

Case     zip     market
1        44485   NA
2        44488   NA
3        43210   NA

There are over 3.5 million records.

Then, I have a second data frame, 'zipcodes'.

market    zip
1         44485
1         44486
1         44488
...       ... (100 zips in market 1)
2         43210
2         43211
...       ... (100 zips in market 2, etc.)

I want to find the correct value for alldata$market for each case based on alldata$zip matching the appropriate value in the zipcode data frame. I'm just looking for the right syntax, and assistance is much appreciated, as usual.

Answer 1

Here's the dplyr way of doing it:

library(tidyverse)
alldata %>%
  select(-market) %>%
  left_join(zipcodes, by="zip")

which, on my machine, is roughly the same performance as lookup.

Answer 2

With such a large data set you may want the speed of an environment lookup. You can use the lookup function from the qdapTools package as follows:

library(qdapTools)
alldata$market <- lookup(alldata$zip, zipcodes[, 2:1])

Or

alldata$zip %l% zipcodes[, 2:1]