dump categorical labels and alternative way to describe category desc

src/model.ts

@@ -1265,13 +1265,19 @@ export class CategoricalColumn extends ValueColumn<string> implements ICategoric
         labels = d3.map<string>();
       desc.categories.forEach((cat, i) => {
         if (typeof cat === 'string') {
+          //just the category value
           cats.push(cat);
         } else {
-          cats.push(cat.name);
+          //the name or value of the category
+          cats.push(cat.name || cat.value);
+          //optional label mapping
           if (cat.label) {
             labels.set(cat.name, cat.label);
           }
-          cols[i] = cat.color;
+          //optional color
+          if (cat.color) {
+            cols[i] = cat.color;
+          }
         }
       });
       this.catLabels = labels;
@@ -1362,6 +1368,9 @@ export class CategoricalColumn extends ValueColumn<string> implements ICategoric
       range: this.colors.range(),
       separator: this.separator
     };
+    if (this.catLabels !== null && !this.catLabels.empty()) {
+      r.labels = this.catLabels.entries();
+    }
     return r;
   }
 
@@ -1371,6 +1380,10 @@ export class CategoricalColumn extends ValueColumn<string> implements ICategoric
     if (dump.colors) {
       this.colors.domain(dump.colors.domain).range(dump.colors.range);
     }
+    if (dump.labels) {
+      this.catLabels = d3.map<string>();
+      dump.labels.forEach((e) => this.catLabels.set(e.key, e.value));
+    }
     this.separator = dump.separator || this.separator;
   }