How to calculate max value for each user and add other attributes

Question

I am trying to get data frame in specific format. I have 3 attributes user_id, movie_id, movie_ranking. I want to display best movie_id and ranking for each user based on the maximal ranking.

I guess dplyr library is good for this, but I cannot really get it work.

Provide [reproducible example](http://stackoverflow.com/questions/5963269) and show some coding effort. — zx8754, Aug 19 '16 at 09:45

score -2 · Accepted Answer · answered Aug 19 '16 at 09:42

-2

With dplyr, we can group by 'user_id', arrange the 'movie_ranking' in descending order and slice the first row.

library(dplyr)
df1 %>%
    group_by(user_id) %>%
    arrange(desc(movie_ranking)) %>%
    slice(1L)

A less efficient option would be using which.max

df1 %>%
    group_by(user_id) %>%
    slice(which.max(movie_ranking))

answered Aug 19 '16 at 09:42

akrun

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works great! thanks akrun! – David Lexa Aug 19 '16 at 12:36

How to calculate max value for each user and add other attributes

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