How to create a data frame from a substring in R?

Question

I have a table which tells me if a client paid in cash or not and what she/he bought:

Client | Item | Cash 
___________________________
John   | CD   | Yes
Billy  | LP   | Yes
Charles| DVD  | 
Mary   | CD   | Yes
Lucy   | Book | 
Sam    | DVD  | 
Louis  | CD   | Yes
Mario  | LP   | Yes 

And then, I want to create a dataframe only with the clients who paid in cash. Like this:

Client | Item | Cash 
___________________________
John   | CD   | Yes
Billy  | LP   | Yes
Mary   | CD   | Yes
Louis  | CD   | Yes
Mario  | LP   | Yes 

I tried this:

df %>%
  group_by(cash) 

Answer 1

You need to filter the rows where the payment is in Cash

library(dplyr)
df %>% filter(Cash=="Yes")

The group_by function is useful if after you want to summarise the data by group (Cash or not): compute sums, counts, means...