Get the mean of first n elements in a column within a dataframe

Question

I am trying to get the mean of the first five elements in a column within a dataframe using the summarize function from the dplyr package. Right now, I am able to get the mean of the entire column but I want to restrict the mean() function to only calculate the first five values in the column.

  mean_5_films <- summarize(
    genre_df,
    average = mean(vote_average, na.rm = TRUE)
  )

Image of dataframe for reference:

It's easier to help you and test possible solutions if you post a minimal [reproducible example](https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example). Pictures of data aren't helpful because we can't copy/paste the data into R — MrFlick, Feb 12 '20 at 20:13

score 3 · Accepted Answer · answered Feb 12 '20 at 20:12

How about

mean_5_films <- summarize(
  genre_df,
  average = mean(head(vote_average,5), na.rm = TRUE)
)

That will take the first 5 vote_average valsues or you could use slice

mean_5_films <- genre_df %>%
  slice(1:5 %>% 
  summarize(average = mean(vote_average, na.rm = TRUE))

score 0 · Answer 2 · answered Feb 12 '20 at 20:17

0

Another option:

mean_5_films <- summarize(
  genre_df,
  average = mean(vote_average[1:5], na.rm = TRUE)
)

answered Feb 12 '20 at 20:17

arg0naut91

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Get the mean of first n elements in a column within a dataframe

2 Answers2