diff --git a/cluster_stats.py b/cluster_stats.py
index 047b2fd..4a19ec2 100644
--- a/cluster_stats.py
+++ b/cluster_stats.py
@@ -137,7 +137,14 @@ def stackplot(ax, x_signal, y_signals, legend_location='best'):
     else:
         # emulating missing Axes.stackplot method
         colors = get_rgb_palette(num_colors=len(y_signals), saturation=1.0, value=0.8)  # ['blue', 'orange', 'green', 'purple', 'yellow', 'cyan']
-        y = np.row_stack(list(y_signals.itervalues()))
+
+        # we sort the signals according to their labels to group departments of the same lab together on the plot
+        ordered_y_signals = []
+        ordered_labels = []
+        for label, y_signal in sorted(y_signals.items()):
+            ordered_y_signals.append(y_signal)
+            ordered_labels.append(label)
+        y = np.row_stack(ordered_y_signals)
         # this call to 'cumsum' (cumulative sum), passing in your y data,
         # is necessary to avoid having to manually order the datasets
         y_stack = np.cumsum(y, axis=0)   # a 3x10 array
@@ -151,9 +158,9 @@ def stackplot(ax, x_signal, y_signals, legend_location='best'):
             ax.add_patch(p)
 
         if legend_location == 'outside right':
-            plt.legend(list(y_signals.keys()), bbox_to_anchor=(1.10, 1.00), loc='upper left')  # force the legend into the bounding box
+            plt.legend(ordered_labels, bbox_to_anchor=(1.10, 1.00), loc='upper left')  # force the legend into the bounding box
         else:
-            plt.legend(list(y_signals.keys()), loc=legend_location)
+            plt.legend(ordered_labels, loc=legend_location)
 
 
 def draw_cluster_value_over_time_graph(inventory, from_date, to_date, graph_type):
@@ -223,7 +230,6 @@ def draw_cluster_value_over_time_graph(inventory, from_date, to_date, graph_type
     ax.xaxis.set_major_formatter(yearsFmt)
     ax.xaxis.set_minor_locator(months)
 
-
     # rotates and right aligns the x labels, and moves the bottom of the
     # axes up to make room for them
     # fig.autofmt_xdate()