Rails: Chartkick cummulative user graph

Question

I'm using chartkick in an active admin dashboard and trying to track a cumulative user base over time.

Using groupdate to count by week I can successfully create a chart displaying point in time counts but struggling to display cumulative results.

Any suggestion on best way to approach as I have not found a similar question?

chart partial

            <%= javascript_include_tag "https://www.gstatic.com/charts/loader.js" %>
            <%= line_chart User.group_by_week(:created_at).count %>

dashboard.rb

            column do
              panel "Recent User Additions" do
                table_for User.order("id desc").limit(10).each do |_user|
                  column(:email)    { |user| link_to(user.email, admin_user_path(user)) }
                  column(:state_waters)    { |user| link_to(user.state_waters, admin_user_path(user)) }
                  column(:state_waters)    { |user| link_to(user.home_port, admin_user_path(user)) }
                end
              end

Answer 1

If I understand your question, you need to manipulate the hash of data.

In controller do somehing like this:

@data = User.group_by_week(:created_at).count
accumulator = 0
@data.transform_values! do |val|
  val += accumulator
  accumulator = val
end

Then show the chart in view as <%= line_chart @data %>

If you inspect the hash <%= User.group_by_week(:created_at).count.inspect %> it becomes clear.

In order to use accumulator over any hash, could be useful to add a custom method to Class hash.

module HashPatch
  def accumulate_values!
    accumulator = 0
    transform_values! do |val|
      val+= accumulator
      accumulator = val
    end
  end
end
Hash.include HashPatch

points = {'x1' => 0, 'x2' => 10, 'x3' => 10, 'x4' => 10.1}
points.accumulate_values! #=> {"x1"=>0, "x2"=>10, "x3"=>20, "x4"=>30.1}

transform_values! since Ruby v4.2.1