Counting the number of cells in a column that contain a specific string (in R)

Question

I have a dataframe in R. I would like to count the number of cells in a column that contain a specific string.

Using the example data below, I want to count how many cells in the column a contain the string "purple." (2)

I imagine something like this: sum(df$a %contains% "purple")

a <- c("red, white", "white", "blue, purple", "purple")
b <- c("white", "white, yellow", "purple", "purple, blue, yellow")
df <- data.table(a, b)

user_14137004 · Answer

You could do with str_count

sum(stringr::str_count(df$a, pattern = "purple"))

user_13460602 · Answer

Use grepl (only works if there are no more than one occurrence per string):

sum(grepl("purple", a))
# [1] 2