R join by tolower

Question

I´ve got some sample data

data1 = data.frame(name = c("cat", "dog", "parrot"), freq = c(1,2,3))
data2 = data.frame(name = c("Cat", "snake", "Dog", freq2 = c(2,3,4)))
data1$name = as.character(data1$name)
data2$name = as.character(data2$name)

which I want to join, but e.g. "cat" and "Cat" should be treated as the same value. I thought of using tolower and first to determine the entries which appear in both data frames by

in_both = data1[(tolower(data1$name) %in% tolower(data2$name)),]

Then I want to join with data2, but that doesn't work because the names doesn't match.

library(dplyr)
left_join(in_both, data2)

Is there a way to join by using tolower?

Answer 1

If you don't want to alter your original data2, as @AshofFire suggested, you can decapitalize the values in name in a pipe %>% and then perform the join operation:

data2 %>%
  mutate(name = str_to_lower(name)) %>%
  inner_join(data1, by = "name") 

  name freq2 freq
1  cat     2    1
2  dog     4    2