fixing cdi.density array length to accommodate both endpoints. n intervals means n + 1 samples.

Author: Austin Martin

src/traces/violin/calc.js

@@ -39,7 +39,7 @@ module.exports = function calc(gd, trace) {
             // step that well covers the bandwidth and is multiple of span distance
             var dist = span[1] - span[0];
             var n = Math.ceil(dist / (bandwidth / 3));
-            var step = (n > 1) ? dist / (n - 1) : 0;
+            var step = dist/ n;
 
             if(!isFinite(step) || !isFinite(n)) {
                 Lib.error('Something went wrong with computing the violin span');
@@ -48,9 +48,10 @@ module.exports = function calc(gd, trace) {
             }
 
             var kde = helpers.makeKDE(cdi, trace, vals);
-            cdi.density = new Array(n);
+            // n intervals means n + 1 sample points to include both endpoints
+            cdi.density = new Array(n + 1);
 
-            for(var k = 0; k < n; k++) {
+            for(var k = 0; k <= n; k++) {
                 var t = span[0] + k * step;
                 var v = kde(t);
                 cdi.density[k] = {v: v, t: t};

test/jasmine/tests/violin_test.js

@@ -402,7 +402,7 @@ describe('Test violin calc:', function() {
         expect(cd[0].bandwidth).toBe(0, 'bandwidth');
     });
 
-    it('should produce exactly n density samples for tiny or near-equal spans', function() {
+    it('should produce exactly n + 1 density samples for tiny or near-equal spans', function() {
         var cd = _calc({
             type: 'violin',
             x: [0, 0],
@@ -413,7 +413,7 @@ describe('Test violin calc:', function() {
         var dist = cdi.span[1] - cdi.span[0];
         var n = Math.ceil(dist / (cdi.bandwidth / 3));
 
-        expect(cdi.density.length).toBe(n);
+        expect(cdi.density.length).toBe(n + 1);
     });
 });