How to select observations in df 1 based on df 2?

[Tung]

Hello, I have 2 data frames. df 1 is called survey. df 2 is called admin. Both data frames contain first name and last name column. I want to select observations in df 1 that they also belong to df 2. (Because I want to know these members explicitly). What is the code?

[smichal]

Hi @Tung,

you could do this e.g. with an inner_join on all relevant columns.

library(tidyverse)
tbl1 <- tibble(FIRST = c("John", "Joe", "Mary"),
               LAST = c("A", "B", "C"),
               MORE = c(34,87,99))
tbl2 <- tibble(FIRST = c("Mary"),
               LAST = c("C"),
               EVEN_MORE = c(111))

# both
inner_join(tbl1, tbl2, by = c("FIRST", "LAST"))
#> # A tibble: 1 x 4
#>   FIRST LAST   MORE EVEN_MORE
#>   <chr> <chr> <dbl>     <dbl>
#> 1 Mary  C        99       111

^{Created on 2020-10-23 by the reprex package (v0.3.0)}

[Tung]

Hi @smichal,

I tried your solution. But

Error: Join columns must be present in data.
x Problem with First name and Last name.
Run rlang::last_error() to see where the error occurred.

[Tung]

@smichal

library(tidyverse)

It's weird. I quit R and reopen R, and your code works. It sees such things always happen in my computer. Why?

[smichal]

Hi @Tung,

sorry, from this point on I could only guess.

Could you make a reproducible example (reprex) to make things clearer?

FAQ: How to do a minimal reproducible example ( reprex ) for beginners

A minimal reproducible example consists of the following items: A minimal dataset, necessary to reproduce the issue The minimal runnable code necessary to reproduce the issue, which can be run on the given dataset, and including the necessary information on the used packages. Let's quickly go over each one of these with examples: Minimal Dataset (Sample Data) You need to provide a data frame that is small enough to be (reasonably) pasted on a post, but big enough to reproduce your issue. Let's say, as an example, that you are working with the iris data frame head(iris) #> Sepal.Length Sepal.Width Petal.Length Petal.Width Species #> 1 5.1 3.5 1.4 0.…

(My guess would be that you have not given the correct column names to join on. )