Calculate average by group based on filter criteria

Question

Apologies for the newbie question, still getting the hang of DPLYR (and R in general).

I have the following dataset, and I am trying to work out the average rating for each area group where there are more than 1 entry.

Area    Rating
UK      5.256
Ireland 6.1465
Canada  6.1452 
USA     6.14
Ireland 4.258
USA     3.154

My expected returned data would be :

Area    Count    Average_Rating 
Ireland 2        5.20255
USA     2        4.647

I have tried the following code, and seem to be falling down when I try to perform the 'count' column (it returns the mean value for all areas)

df %>%
 group_by (Area) %>%
 mutate (count =n()) %>%
 summarise (mean = mean(Average_Rating)) %>%
 arrange(desc(mean))

I have tried playing about with the order of the verbs with no success. Any help greatly appreciated!

Answer 1

We need a filter after the group_by step

library(dplyr)
df1 %>%
   group_by(Area) %>%
   filter(n() > 1) %>%
   summarise(Count = n(), Average_Rating = mean(Rating)) %>%
   arrange(desc(Average_Rating))
# A tibble: 2 x 3
#  Area    Count Average_Rating
#  <chr>   <int>          <dbl>
#1 Ireland     2           5.20
#2 USA         2           4.65

data

df1 <- structure(list(Area = c("UK", "Ireland", "Canada", "USA", "Ireland", 
"USA"), Rating = c(5.256, 6.1465, 6.1452, 6.14, 4.258, 3.154)), 
class = "data.frame", row.names = c(NA, 
-6L))