Suport minUnit for time scale

When dealing with time-delineated datasets, often we have data for known
intervals of time. For example, we may have a dataset which represents number
of purchases per day:

```json
{
	labels: ['2016-01-01', '2016-01-02', '2016-01-03']
	datasets: [
		{
			data: [12, 87, 42]
		}
	],
	'...': '...'
}
```

In this case, Chart.js will attempt to figure out the best interval to display
the data, and could pick `hours` as the unit. However, in this case, we would
prefer to just use the `days` interval since our data's granularity can not be
represented well with `hours`.

To remedy this, this commit adds the `minUnit` option which allows
users to (optionally) specify what the minimum unit they would like
to use.

diff --git a/docs/02-Scales.md b/docs/02-Scales.md
index 813b44c154f7418c3bb3bdce60c026805e62fdb6..c776355ebc79603a2a0b3b1d26c3ae1527e1d420 100644 (file)
--- a/docs/02-Scales.md
+++ b/docs/02-Scales.md
@@ -224,6 +224,7 @@ round | String | - | If defined, dates will be rounded to the start of this unit
 tooltipFormat | String | '' | The moment js format string to use for the tooltip.
 unit | String | - | If defined, will force the unit to be a certain type. See [Time Units](#scales-time-units) section below for details.
 unitStepSize | Number | 1 | The number of units between grid lines.
+minUnit | String | 'millisecond' | The minimum display format to be used for a time unit
 
 #### Date Formats
 

diff --git a/src/scales/scale.time.js b/src/scales/scale.time.js
index ab935a12a0a0ca1f5157c67bc7a8a8ec6dc3bfe1..2c20bd8c59ffce1d3c4285d8bef9d407d6e67572 100755 (executable)
--- a/src/scales/scale.time.js
+++ b/src/scales/scale.time.js
@@ -48,6 +48,7 @@ module.exports = function(Chart) {
                        round: false, // none, or override with week, month, year, etc.
                        displayFormat: false, // DEPRECATED
                        isoWeekday: false, // override week start day - see http://momentjs.com/docs/#/get-set/iso-weekday/
+                       minUnit: 'millisecond',
 
                        // defaults to unit's corresponding unitFormat below or override using pattern string from http://momentjs.com/docs/#/displaying/format/
                        displayFormats: {
@@ -195,7 +196,7 @@ module.exports = function(Chart) {
                                var labelCapacity = innerWidth / (tickLabelWidth);
 
                                // Start as small as possible
-                               me.tickUnit = 'millisecond';
+                               me.tickUnit = me.options.time.minUnit;
                                me.scaleSizeInUnits = me.lastTick.diff(me.firstTick, me.tickUnit, true);
                                me.displayFormat = me.options.time.displayFormats[me.tickUnit];
 

diff --git a/test/scale.time.tests.js b/test/scale.time.tests.js
index 8a3852a8c05524cedbf542af96989445b4e657d6..930ef254c9ded082b38d5b8ee5503ac570a5a41c 100755 (executable)
--- a/test/scale.time.tests.js
+++ b/test/scale.time.tests.js
@@ -84,6 +84,7 @@ describe('Time scale tests', function() {
                                round: false,
                                isoWeekday: false,
                                displayFormat: false,
+                               minUnit: 'millisecond',
                                displayFormats: {
                                        'millisecond': 'h:mm:ss.SSS a', // 11:20:01.123 AM
                                        'second': 'h:mm:ss a', // 11:20:01 AM
@@ -279,6 +280,31 @@ describe('Time scale tests', function() {
                expect(scale.ticks).toEqual(['Jan 1, 8PM', 'Jan 1, 9PM', 'Jan 1, 10PM', 'Jan 1, 11PM', 'Jan 2, 12AM', 'Jan 2, 1AM', 'Jan 2, 2AM', 'Jan 2, 3AM', 'Jan 2, 4AM', 'Jan 2, 5AM', 'Jan 2, 6AM', 'Jan 2, 7AM', 'Jan 2, 8AM', 'Jan 2, 9AM', 'Jan 2, 10AM', 'Jan 2, 11AM', 'Jan 2, 12PM', 'Jan 2, 1PM', 'Jan 2, 2PM', 'Jan 2, 3PM', 'Jan 2, 4PM', 'Jan 2, 5PM', 'Jan 2, 6PM', 'Jan 2, 7PM', 'Jan 2, 8PM', 'Jan 2, 9PM']);
        });
 
+       it('build ticks honoring the minUnit', function() {
+               var scaleID = 'myScale';
+
+               var mockData = {
+                       labels: ["2015-01-01T20:00:00", "2015-01-02T21:00:00"], // days
+               };
+
+               var mockContext = window.createMockContext();
+               var config = Chart.helpers.clone(Chart.scaleService.getScaleDefaults('time'));
+               config.time.minUnit = 'day';
+               var Constructor = Chart.scaleService.getScaleConstructor('time');
+               var scale = new Constructor({
+                       ctx: mockContext,
+                       options: config, // use default config for scale
+                       chart: {
+                               data: mockData
+                       },
+                       id: scaleID
+               });
+
+               //scale.buildTicks();
+               scale.update(400, 50);
+               expect(scale.ticks).toEqual(['Jan 1, 2015', 'Jan 2, 2015', 'Jan 3, 2015']);
+       });
+
        it('should build ticks using the config diff', function() {
                var scaleID = 'myScale';