Cumulative sum by month

Ruby
1

Hey all,

While it is possible to doc cumulative sum by month in mysql using MONTH
and COUNT statements, I’m trying to figure out if the same kind of
statement is available in ruby, something like a substitute for the
month value I put below:

def cumulative_sum
values = [:passed_on, :failed_on, :incompleted_on]
sum = 0
case values
when :passed_on
month.each do |state|
while state > ‘2010-03-00’
@passed_on = state.map{ |x| sum += x}
end
end

 when :failed_on
    month.each do |state|
    while state > '2010-03-00'
      @failed_on = state.map{ |x| sum += x}
    end
    end

  when :incompleted_on
     month.each do |state|
     while state > '2010-03-00'
       @incompleted_on = state.map{ |x| sum += x}
     end
     end
     end

end

Note that the passed_on, failed_on and incompleted_on fields of students
table are data typed as date.
Thanks for any response.