Ruby on Rails field average?

ruby-on-rails ruby collections average
David picture David · Jun 12, 2009 · Viewed 9.2k times · Source

Is there an easy way to obtain the average of an attribute in a collection?

For instance, each user has a score.

Given a collection of user(s) (@users), how can you get the average score for the group?

Is there anything like @users.average(:score)? I think I came across something like this for database fields, but I need it to work for a collection...

Answer

Ryan Oberoi picture Ryan Oberoi · Jun 12, 2009

For your question, one could actually do:

@users.collect(&:score).sum.to_f/@users.length if @users.length > 0

Earlier I thought, @users.collect(&:score).average would have worked. For database fields, User.average(:score) will work. You can also add :conditions like other activerecord queries.

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