application_helper.rb

  def week_stat model
    table = model.name.tableize
    from = Time.now - 7.days

    query = "
      select created_at, count(*)
      from #{table}
      where created_at > '#{from}'
      group by created_at
    "
    wstat =  ActiveRecord::Base.connection.select query
    binding.pry
  end