test.rb

def self.me2
  total_count = 0
  total_new = Project.order(datum: :asc).group("date_format(datum, '%Y%m')").count.select{|d,c| d}
  total_by_month = Hash[total_new.map { |month, n| [ month, total_count += n ]}]
end
 
def self.mike
  new_users_by_month = Project.group("date_format(datum, '%Y%m')").count.select{|d,c| d}
  total_users_by_month = Hash[new_users_by_month.map do |d, c|
    [d, new_users_by_month.sum do |d2,c|
      d2 <= d ? c : 0
    end]
  end]
end