diff --git a/src/plots/attributes.js b/src/plots/attributes.js
index 69496df0ee3..e8f9d6f717f 100644
--- a/src/plots/attributes.js
+++ b/src/plots/attributes.js
@@ -28,6 +28,14 @@ module.exports = {
             '(provided that the legend itself is visible).'
         ].join(' ')
     },
+    groups: {
+        valType: 'data_array',
+        description: [
+            'An array of strings corresponding to each respective datum. These strings are not' +
+            'inherently used by plotly for any purpose but may be used, for example, with transforms' +
+            'in order to filter or group points by an auxilliary property.'
+        ].join(' ')
+    },
     showlegend: {
         valType: 'boolean',
         role: 'info',
diff --git a/src/plots/plots.js b/src/plots/plots.js
index 56aa8a9b696..13b5ddeceb7 100644
--- a/src/plots/plots.js
+++ b/src/plots/plots.js
@@ -742,6 +742,7 @@ plots.supplyTraceDefaults = function(traceIn, traceIndex, layout) {
     coerce('type');
     coerce('uid');
     coerce('name', 'trace ' + traceIndex);
+    coerce('groups');
 
     // coerce subplot attributes of all registered subplot types
     var subplotTypes = Object.keys(subplotsRegistry);
diff --git a/src/traces/scatter/attributes.js b/src/traces/scatter/attributes.js
index d9f83dd78ce..dbc7b15cd36 100644
--- a/src/traces/scatter/attributes.js
+++ b/src/traces/scatter/attributes.js
@@ -67,7 +67,11 @@ module.exports = {
     },
     ids: {
         valType: 'data_array',
-        description: 'A list of keys for object constancy of data points during animation'
+        description: [
+            'A list of unique string ids for object constancy of data points during animation.' +
+            'For efficiency, the uniqueness of ids is not validated, but unexpected results may' +
+            'occur if ids are not unique. *ids* is equivalent to a *key* in d3.'
+        ].join(' ')
     },
     text: {
         valType: 'string',
diff --git a/src/traces/scatter/calc.js b/src/traces/scatter/calc.js
index e7df798f1fd..cc91bdd14d6 100644
--- a/src/traces/scatter/calc.js
+++ b/src/traces/scatter/calc.js
@@ -117,7 +117,9 @@ module.exports = function calc(gd, trace) {
             {x: x[i], y: y[i]} : {x: false, y: false};
 
         if(trace.ids) {
-            cd[i].id = String(trace.ids[i]);
+            if(trace.ids[i] !== undefined && trace.ids[i] !== null) {
+                cd[i].id = String(trace.ids[i]);
+            }
         }
     }
 
diff --git a/src/transforms/filter.js b/src/transforms/filter.js
index 042798ac4ef..8699a16684f 100644
--- a/src/transforms/filter.js
+++ b/src/transforms/filter.js
@@ -164,9 +164,13 @@ function getDataToCoordFunc(gd, trace, filtersrc) {
     // -> use setConvert method
     if(ax) return ax.d2c;
 
-    // special case for 'ids'
+    // special case for 'ids' or 'groups'
     // -> cast to String
-    if(filtersrc === 'ids') return function(v) { return String(v); };
+    if(['ids', 'groups'].indexOf(filtersrc) !== -1) {
+        return function(v) {
+            return v === undefined ? undefined : String(v);
+        };
+    }
 
     // otherwise
     // -> cast to Number
diff --git a/test/jasmine/tests/calcdata_test.js b/test/jasmine/tests/calcdata_test.js
index 9ac9dda0e98..b4ee7ffd0ee 100644
--- a/test/jasmine/tests/calcdata_test.js
+++ b/test/jasmine/tests/calcdata_test.js
@@ -30,6 +30,17 @@ describe('calculated data and points', function() {
         });
     });
 
+    describe('ids', function() {
+        it('should assign ids to points and cast them to strings in the process', function() {
+            Plotly.plot(gd, [{ x: [1, 2, 3, 5], y: [1, null, 3, 5], ids: [1, 'a', 'b', undefined]}], {});
+
+            expect(gd.calcdata[0][0]).toEqual(jasmine.objectContaining({ x: 1, y: 1, id: '1'}));
+            expect(gd.calcdata[0][1]).toEqual(jasmine.objectContaining({ x: false, y: false, id: 'a'}));
+            expect(gd.calcdata[0][2]).toEqual(jasmine.objectContaining({ x: 3, y: 3, id: 'b'}));
+            expect(gd.calcdata[0][3]).toEqual(jasmine.objectContaining({ x: 5, y: 5}));
+        });
+    });
+
     describe('category ordering', function() {
 
         describe('default category ordering reified', function() {