AxisTypes has a better toString method

pdb-js/src/app/visualization-page/visualization-page.component.ts

@@ -99,13 +99,17 @@ export class VisualizationPageComponent implements OnInit {
   
   getAxes() : AxesTypes {
     
-    var x = new Set<DataType>();
-    var y = new Set<DataType>();
+    var x = new Array<DataType>();
+    var y = new Array<DataType>();
     
     for(var i = 0; i < this.selectedPlotType.length; i++){
       var plotType = this.selectedPlotType[i];
-      x.add(plotType.xAxis);
-      y.add(plotType.yAxis);
+      if (!x.includes(plotType.xAxis)) {
+        x.push(plotType.xAxis);
+      }
+      if (!y.includes(plotType.yAxis)) {
+        y.push(plotType.yAxis);
+      }
     }
     
     return new AxesTypes(x,y);
@@ -233,6 +237,11 @@ export class DateRange {
   startDate: any;
   endDate: any;
   duration: any;
-      
-  
+}
+
+export class AxesUsed {
+  x1: DataType;
+  y1: DataType;
+  x2: DataType;
+  y2: DataType;
 }