Use gruff gem to generate bar graphs

app/models/cost.rb

@@ -1,5 +1,7 @@
 require 'open-uri'
-require 'gr/plot'
+require 'i18n'
+require 'gruff'
+
 EASY_ENERGY_TARIFFS = {}
 
 # See https://www.belastingdienst.nl/wps/wcm/connect/bldcontentnl/belastingdienst/zakelijk/overige_belastingen/belastingen_op_milieugrondslag/tarieven_milieubelastingen/tabellen_tarieven_milieubelastingen
@@ -20,6 +22,11 @@ class Cost
     @entsoe = Entsoe.new(zone, storage_cost)
     @max_charge_kwh =  max_charge
     @battery = Battery.new(battery_capacity)
+
+    # Allow for Dutch titles in graphs
+    I18n.load_path += Dir[File.expand_path("config/locales") + "/*.yml"]
+    I18n.available_locales = [:en, :nl]
+    I18n.locale = :nl
   end
   
   # Government reduced VAT to 9% from 1 July 2022 until 31 Dec 2022
@@ -98,12 +105,16 @@ class Cost
   def easy_energy_tariff_barplot(date)
     hours = (0..23).to_a
     costs = easy_energy_hours(date)
-    GR.barplot(hours,costs)
-    # make sure you have set GKS_WSTYPE=100 in the environment (for headless setup)
-    title = "Tarief per kwH (incl. belastingen en BTW) - %s" % date.strftime("%A, %e %B %Y")
-    xlabel = "uur"
-    ylabel = "EUR"
-    GR.savefig("plots/easy_tariff_%s.png" % date.strftime("%F"), title: title, xlabel: xlabel, ylabel: ylabel)
+    g = Gruff::StackedBar.new()
+    g.title = "Tarief per kwH (incl. belastingen en BTW) - %s" % I18n.localize(date, format: "%A, %e %B %Y")
+    g.x_axis_label = "uur"
+    #g.y_axis_label = "EUR"
+    g.y_axis_label_format = lambda do |value|
+      "€ %.2f" % value
+    end
+    g.labels = hours
+    g.data :costs, costs
+    g.write("plots/easy_tariff_%s.png" % date.strftime("%F"))
   end
   
   def easy_energy_cost_barplot(date)
@@ -126,13 +137,17 @@ class Cost
     
     # create plot
     hours = (0..23).to_a
-    GR.barplot(hours,costs)
-    # make sure you have set GKS_WSTYPE=100 in the environment (for headless setup)
-    title = "Verbruikskosten (incl. belastingen en BTW) - %s" % date.strftime("%A, %e %B %Y")
-    xlabel = "uur"
-    ylabel = "EUR"
-    GR.savefig("plots/easy_cost_%s.png" % date.strftime("%F"), title: title, xlabel: xlabel, ylabel: ylabel)
-
+    g = Gruff::StackedBar.new()
+    g.title = "Verbruikskosten (incl. belastingen en BTW) - %s" % I18n.localize(date, format: "%A, %e %B %Y")
+    g.x_axis_label = "uur"
+    #g.y_axis_label = "EUR"
+    g.y_axis_label_format = lambda do |value|
+      "€ %.2f" % value
+    end
+    g.labels = hours
+    g.data :costs, costs
+    g.write("plots/easy_tariff_%s.png" % date.strftime("%F"))
+    
     # return the sum cost
     costs.sum
   end