R - Count the number of times a value appears in a column using dplyr-CodePudding

I have a dataframe x in R

ID Name Code
1  John aa1
1  Sue  aa2
1  Mike aa2
1  Karl aa3
1  Lucy aa1

I would like to add an extra column to this dataframe counting the number of times each Code value appears:

ID Name Code Code_frequency
1  John aa1  1
1  Sue  aa2  2
1  Mike aa2  2
1  Karl aa3  1
1  Lucy aa4  1

I've tried using various combinations of mutate and count but I get error messages saying that I've used the wrong data type: no applicable method for 'count' applied to an object of class "character"

I've also seen that dplyr has the summarise function but I need to preserve the layout of the dataframe as this will be exported from R as each row needs to be manually checked.

Is there a way to do this in R? A dplyr solution would fit easily into the rest of the code I have but I would welcome suggestions from other libraries as well.

CodePudding user response：

Using the n() function:

x %>%
  group_by(Code) %>%
  mutate(Code_frequency = n()) %>%
  ungroup()