added include_null_class_rows

README.md

@@ -41,7 +41,12 @@ const results = calculate({
   // deletes zonal features that have no overlap with the classes
   // examples include districts not covered by a hurricane
   // or cities that can't feel an earthquake
-  remove_features_with_no_overlap: true
+  remove_features_with_no_overlap: true,
+
+  // default is true
+  // set to false to filter out table rows for
+  // parts of zones that don't intersect a class
+  include_null_class_rows: true
 });
 ```
 result is the following object:

index.js

@@ -64,6 +64,7 @@ function calculate({
   class_geometry_type,
   include_zero_count = false,
   include_zero_area = false,
+  include_null_class_rows = true,
   class_properties_delimiter = ",",
   preserve_features = true,
   remove_features_with_no_overlap = false,
@@ -249,6 +250,10 @@ function calculate({
     // convert class id from string to array
     class_id = JSON.parse(class_id);
 
+    if (include_null_class_rows === false && class_id === null) {
+      continue;
+    }
+
     const row = {};
     zone_id.map((it, i) => {
       const key = Array.isArray(zone_properties) ? zone_properties[i] : "index";

test.js

@@ -328,16 +328,23 @@ test("percentage within range when using class property", ({ eq }) => {
   });
 });
 
-test("delete zone features that don't overlap classes", ({ eq }) => {
+test("ignore parts of zones that don't overlap classes", ({ eq }) => {
   const result = calculate({
     zones: louisiana_parishes,
     zone_properties: ["ParishName"],
     classes: cone_120km,
     class_properties: ["wind_speed"],
     preserve_features: false,
-    remove_features_with_no_overlap: true
+    remove_features_with_no_overlap: true,
+    include_null_class_rows: false
   });
   eq(louisiana_parishes.features.length > result.geojson.features.length, true);
   eq(louisiana_parishes.features.length, 64);
   eq(result.geojson.features.length, 22);
+  eq(result.table.columns, ["zone:ParishName", "class:wind_speed", "stat:area", "stat:percentage"]);
+  eq(result.table.rows.length, 22);
+  eq(
+    result.table.rows.every(row => row["stat:area"] > 0),
+    true
+  );
 });