Question

I have a setup in which there are 10 attributes that accept a float in a rails form. Each attribute also is associated with a value in my model. If a number is entered on the form for more than one attribute, I need to create a weighted average.

An example would be if I have 10 products, each having a price in my model. In the form, a user can enter in the amount (number of products) for each product. I’d like to calculate a weighted price for those products that have an amount entered.

So how can I create a weighted average that checks which products have amounts entered?

Answer 1

columns_names = ['a','b','c','d'] # array of name of the columns

obj = Model.find(:id) # find the object with id

# loop and get column values that are set

values = columns_names.inject([]) do |arr,column_name|
  arr << obj.column_name if params[column_name].eql?"true" # collect the values if the column set
  arr
end

#get average
if values.blank?
  # no column selected
else
  avg =  values.reduce(:+)/values.size
end

check this for help on weighted average

http://www.dzone.com/snippets/weighted-mean