add support for histogram* traces on multicategory axes

src/plots/cartesian/axes.js

@@ -278,8 +278,7 @@ axes.autoBin = function(data, ax, nbins, is2d, calendar, size) {
     var dataMin = Lib.aggNums(Math.min, null, data);
     var dataMax = Lib.aggNums(Math.max, null, data);
 
-    // TODO multicategory, if we allow multicategory histograms
-    if(ax.type === 'category') {
+    if(ax.type === 'category' || ax.type === 'multicategory') {
         return {
             start: dataMin - 0.5,
             end: dataMax + 0.5,

src/traces/histogram/calc.js

@@ -270,7 +270,8 @@ function calcAllAutoBins(gd, trace, pa, mainData, _overlayEdgeCase) {
 
         // Edge case: single-valued histogram overlaying others
         // Use them all together to calculate the bin size for the single-valued one
-        if(isOverlay && newBinSpec._dataSpan === 0 && pa.type !== 'category') {
+        if(isOverlay && newBinSpec._dataSpan === 0 &&
+            pa.type !== 'category' && pa.type !== 'multicategory') {
             // Several single-valued histograms! Stop infinite recursion,
             // just return an extra flag that tells handleSingleValueOverlays
             // to sort out this trace too
@@ -327,7 +328,7 @@ function calcAllAutoBins(gd, trace, pa, mainData, _overlayEdgeCase) {
             Lib.aggNums(Math.min, null, pos0);
 
         var dummyAx = {
-            type: pa.type === 'category' ? 'linear' : pa.type,
+            type: (pa.type === 'category' || pa.type === 'multicategory') ? 'linear' : pa.type,
             r2l: pa.r2l,
             dtick: binOpts.size,
             tick0: mainStart,

src/traces/histogram/defaults.js

@@ -36,7 +36,9 @@ module.exports = function supplyDefaults(traceIn, traceOut, defaultColor, layout
     var sampleLetter = orientation === 'v' ? 'x' : 'y';
     var aggLetter = orientation === 'v' ? 'y' : 'x';
 
-    var len = (x && y) ? Math.min(x.length && y.length) : (traceOut[sampleLetter] || []).length;
+    var len = (x && y) ?
+        Math.min(Lib.minRowLength(x) && Lib.minRowLength(y)) :
+        Lib.minRowLength(traceOut[sampleLetter] || []);
 
     if(!len) {
         traceOut.visible = false;

src/traces/histogram2d/sample_defaults.js

@@ -6,24 +6,26 @@
 * LICENSE file in the root directory of this source tree.
 */
 
-
 'use strict';
 
 var Registry = require('../../registry');
+var Lib = require('../../lib');
 
 module.exports = function handleSampleDefaults(traceIn, traceOut, coerce, layout) {
     var x = coerce('x');
     var y = coerce('y');
+    var xlen = Lib.minRowLength(x);
+    var ylen = Lib.minRowLength(y);
 
     // we could try to accept x0 and dx, etc...
     // but that's a pretty weird use case.
     // for now require both x and y explicitly specified.
-    if(!(x && x.length && y && y.length)) {
+    if(!(x && xlen && y && ylen)) {
         traceOut.visible = false;
         return;
     }
 
-    traceOut._length = Math.min(x.length, y.length);
+    traceOut._length = Math.min(xlen, ylen);
 
     var handleCalendarDefaults = Registry.getComponentMethod('calendars', 'handleTraceDefaults');
     handleCalendarDefaults(traceIn, traceOut, ['x', 'y'], layout);

test/image/mocks/multicategory_histograms.json

@@ -0,0 +1,121 @@
+{
+  "data": [
+    {
+      "type": "histogram2d",
+      "name": "hist2d",
+      "x": [
+        [ 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018 ],
+        [ "a", "a", "a", "a", "a", "a", "b", "b", "c", "c", "c", "c" ]
+      ],
+      "y": [
+        [ 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2018, 2017, 2017 ],
+        [ "a", "a", "a", "a", "a", "a", "b", "b", "c", "c", "c", "c", "b", "c", "a" ]
+      ],
+      "colorscale": "Viridis",
+      "opacity": 0.8,
+      "colorbar": {
+        "x": 0.7,
+        "xanchor": "left",
+        "y": 0.7,
+        "yanchor": "bottom",
+        "len": 0.3,
+        "title": {
+          "side": "right",
+          "text": "hist2d"
+        }
+      }
+    },
+    {
+      "mode": "markers",
+      "x": [
+        [ 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018 ],
+        [ "a", "a", "a", "a", "a", "a", "b", "b", "c", "c", "c", "c" ]
+      ],
+      "y": [
+        [ 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2018, 2017, 2017 ],
+        [ "a", "a", "a", "a", "a", "a", "b", "b", "c", "c", "c", "c", "b", "c", "a" ]
+      ],
+      "marker": {
+        "color": "#d3d3d3",
+        "size": 18,
+        "opacity": 0.3,
+        "line": {"color": "black", "width": 1}
+      }
+    },
+
+    {
+      "type": "histogram2dcontour",
+      "name": "hist2dcontour",
+      "x": [
+        [ 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018 ],
+        [ "a", "a", "a", "a", "a", "a", "b", "b", "c", "c", "c", "c" ]
+      ],
+      "y": [
+        [ 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2018, 2017, 2017 ],
+        [ "a", "a", "a", "a", "a", "a", "b", "b", "c", "c", "c", "c", "b", "c", "a" ]
+      ],
+      "contours": {
+        "coloring": "lines"
+      },
+      "line": {
+        "width": 4
+      },
+      "colorscale": "Viridis",
+      "colorbar": {
+        "x": 1,
+        "xanchor": "right",
+        "y": 0.7,
+        "yanchor": "bottom",
+        "len": 0.3,
+        "title": {
+          "side": "right",
+          "text": "hist2dcontour"
+        }
+      }
+    },
+    {
+      "type": "histogram",
+      "name": "hist-x",
+      "x": [
+        [ 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018 ],
+        [ "a", "a", "a", "a", "a", "a", "b", "b", "c", "c", "c", "c" ]
+      ],
+      "yaxis": "y2",
+      "marker": {
+        "color": "#008080"
+      }
+    },
+    {
+      "type": "histogram",
+      "name": "hist-y",
+      "y": [
+        [ 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2017, 2018, 2018, 2017, 2017 ],
+        [ "a", "a", "a", "a", "a", "a", "b", "b", "c", "c", "c", "c", "b", "c", "a" ]
+      ],
+      "xaxis": "x2",
+      "marker": {
+        "color": "#008080"
+      }
+    }
+  ],
+  "layout": {
+    "title": {
+      "text": "Multi-category histograms",
+      "xref": "paper",
+      "x": 0
+    },
+    "xaxis": {
+      "domain": [0, 0.65]
+    },
+    "yaxis": {
+      "domain": [0, 0.65]
+    },
+    "xaxis2": {
+      "domain": [0.7, 1]
+    },
+    "yaxis2": {
+      "domain": [0.7, 1]
+    },
+    "showlegend": false
+  }
+}