eggman2001 wrote: > I have a few thousand rows of stock market data - one row for each > day. I'm using ActiveRecord to perform database operations. > > I'm interested in performing a calculation on each row while > incorporating the result of the calculation on the previous row, and > then once the calculation has been performed for all rows, perform a > new calculation that uses the individual calculations of each row. > > I figure that I'll start with an array of size 3,000. Then I would > probably want to iterate over it, possibly saving the result of the > operation of each row to a new array but this area is a little foggy. > > Any suggestions?
Assuming you want to calculate something like percent change for each day, you could load the entire result set into an array, and then do something like: changes = @stock_data.each_with_object([]) do |data, array| last_value = array.last.value change = (data.value - last_value) / last_value * 100 unless last_value.zero? array << [data.transaction_date, change] end -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
