Select and plot top frequencies with dplyr

Question

The objective is to select/filter top 3 (or n) events that have the largest frequencies (occurrences) in a dataframe then plot these using a barplot in ggplot2.

The example:

library(dplyr)
df <- data.frame(
  type=c("car","bike","horse","boat","yacht","train"),freq=c(20,2,5,60,11,10))

So far, I could arrange df:

df_order <- df %>% 
            arrange(desc(freq))
[1] df_order
type freq
1  boat   60
2   car   20
3 yacht   11
4 train   10
5 horse    5
6  bike    2 

The desired result is to select only the top 3 types then plot these using a barplot. I think count will be useful, but not sure how to do that. Any ideas?

Solution

After we order the dataset based on the 'freq' column (arrange(...)), we can the top 3 values with slice, use ggplot, specify the 'x' and 'y' variables in the aes, and plot the bar with geom_bar

 library(ggplot2)
 library(dplyr)
 df %>% 
    arrange(desc(freq)) %>%
    slice(1:3) %>%
    ggplot(., aes(x=type, y=freq))+
              geom_bar(stat='identity')

Or another option is top_n which is a convenient wrapper that uses filter and min_rank to select the top 'n' (3) observations in 'freq' column and use ggplot as above.

top_n(df, n=3, freq) %>%
          ggplot(., aes(x=type, y=freq))+
              geom_bar(stat='identity')