allow charts to have Y-axis min and max specified

app/views/charts/_config.html.erb

@@ -144,6 +144,14 @@
       <td><%= t(:chart_max) %>: </td>
       <td><input type="text" class="chart_options<%= index %> shortfield" id="max_<%= index %>" /></td>
     </tr>
+    <tr>
+      <td><%= t(:chart_yaxis_min) %>: </td>
+      <td><input type="text" class="chart_options<%= index %> shortfield" id="yaxismin_<%= index %>" /></td>
+    </tr>
+    <tr>
+      <td><%= t(:chart_yaxis_max) %>: </td>
+      <td><input type="text" class="chart_options<%= index %> shortfield" id="yaxismax_<%= index %>" /></td>
+    </tr>
     <tr>
       <td><input type="button" id="button<%= index %>" value="<%= t(:chart_update) %>" /></td>
       <td></td>

app/views/charts/show.html.erb

@@ -149,9 +149,11 @@
               }
           },
           yAxis: {
-              title: {
-            text: ''
-              }
+            title: {
+              text: ''
+            },
+            min: <%= params[:yaxismin].present? ? params[:yaxismin] : 'null '%>,
+            max: <%= params[:yaxismax].present? ? params[:yaxismax] : 'null' %>
           },
           exporting: {
               enabled: <%= (params[:export].present? && params[:export] == 'true') ? 'true' : 'false' %>

app/views/docs/charts.html.erb

@@ -33,6 +33,8 @@
       <li><b>dynamic</b> (true/false) Make chart update automatically every 15 seconds, default: false (optional)</li>
       <li><b>step</b> (true/false) Draw chart as a step chart, default: false (optional)</li>
       <li><b>export</b> (true/false) Show export buttons, so that chart can be saved as an image, default: false (optional)</li>
+      <li><b>yaxismin</b> (decimal) Minimum value of chart's Y-Axis; if blank the value is auto-calculated (optional)</li>
+      <li><b>yaxismax</b> (decimal) Maximum value of chart's Y-Axis; if blank the value is auto-calculated (optional)</li>
     </ul>
 
     <br>