referring to variables by name in selecting functions

[siddharthprabhu]

@fredoxvii

.data takes the data.frame from the previous pipe, where as . takes the original data set that begins the pipe. This matters if you have several filters, mutations, and summaries as you pipe your data along. Just an FYI if you see the . in code.

This understanding is incorrect. . refers to the object on the LHS of the "current stage" of the pipe. It does not refer to the original data set at the start of the pipeline. You can verify this with the following code.

library(dplyr, warn.conflicts = FALSE)
#> Warning: package 'dplyr' was built under R version 4.0.4

# If . referred to the original data.frame, this code should work. But it does not.
iris %>% 
  select(-Species) %>% 
  rename(Species_new = .[[Species]])
#> Error: object 'Species' not found

^{Created on 2021-03-21 by the reprex package (v1.0.0)}

@fredoxvii

Since you brought up the .data pronoun, do you know the difference between .data and . ?

.data is a pronoun; a special construct which is used to disambiguate between data variables and environment variables. See this post for a detailed write-up on this topic.