Fix and regression test for Issue 147: X-axis date labels break after DST transitions
[dygraphs.git] / dygraph-tickers.js
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1/**
2 * @license
3 * Copyright 2011 Dan Vanderkam (danvdk@gmail.com)
4 * MIT-licensed (http://opensource.org/licenses/MIT)
5 */
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6
7/**
8 * @fileoverview Description of this file.
9 * @author danvk@google.com (Dan Vanderkam)
10 *
11 * A ticker is a function with the following interface:
12 *
13 * function(a, b, pixels, options_view, dygraph, forced_values);
14 * -> [ { v: tick1_v, label: tick1_label[, label_v: label_v1] },
15 * { v: tick2_v, label: tick2_label[, label_v: label_v2] },
16 * ...
17 * ]
18 *
19 * The returned value is called a "tick list".
20 *
21 * Arguments
22 * ---------
23 *
24 * [a, b] is the range of the axis for which ticks are being generated. For a
25 * numeric axis, these will simply be numbers. For a date axis, these will be
26 * millis since epoch (convertable to Date objects using "new Date(a)" and "new
27 * Date(b)").
28 *
29 * opts provides access to chart- and axis-specific options. It can be used to
30 * access number/date formatting code/options, check for a log scale, etc.
31 *
32 * pixels is the length of the axis in pixels. opts('pixelsPerLabel') is the
33 * minimum amount of space to be allotted to each label. For instance, if
34 * pixels=400 and opts('pixelsPerLabel')=40 then the ticker should return
35 * between zero and ten (400/40) ticks.
36 *
37 * dygraph is the Dygraph object for which an axis is being constructed.
38 *
39 * forced_values is used for secondary y-axes. The tick positions are typically
40 * set by the primary y-axis, so the secondary y-axis has no choice in where to
41 * put these. It simply has to generate labels for these data values.
42 *
43 * Tick lists
44 * ----------
45 * Typically a tick will have both a grid/tick line and a label at one end of
46 * that line (at the bottom for an x-axis, at left or right for the y-axis).
47 *
48 * A tick may be missing one of these two components:
49 * - If "label_v" is specified instead of "v", then there will be no tick or
50 * gridline, just a label.
51 * - Similarly, if "label" is not specified, then there will be a gridline
52 * without a label.
53 *
54 * This flexibility is useful in a few situations:
55 * - For log scales, some of the tick lines may be too close to all have labels.
56 * - For date scales where years are being displayed, it is desirable to display
57 * tick marks at the beginnings of years but labels (e.g. "2006") in the
58 * middle of the years.
59 */
60
83b0c192 61/*jshint globalstrict:true, sub:true */
758a629f 62/*global Dygraph:false */
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63"use strict";
64
b2867ee1 65/** @typedef {Array.<{v:number, label:string, label_v:(string|undefined)}>} */
0cd1ad15 66Dygraph.TickList = undefined; // the ' = undefined' keeps jshint happy.
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67
68/** @typedef {function(
69 * number,
70 * number,
71 * number,
72 * function(string):*,
73 * Dygraph=,
74 * Array.<number>=
75 * ): Dygraph.TickList}
76 */
0cd1ad15 77Dygraph.Ticker = undefined; // the ' = undefined' keeps jshint happy.
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78
79/** @type {Dygraph.Ticker} */
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80Dygraph.numericLinearTicks = function(a, b, pixels, opts, dygraph, vals) {
81 var nonLogscaleOpts = function(opt) {
82 if (opt === 'logscale') return false;
83 return opts(opt);
84 };
85 return Dygraph.numericTicks(a, b, pixels, nonLogscaleOpts, dygraph, vals);
86};
87
b2867ee1 88/** @type {Dygraph.Ticker} */
48e614ac 89Dygraph.numericTicks = function(a, b, pixels, opts, dygraph, vals) {
b2867ee1 90 var pixels_per_tick = /** @type{number} */(opts('pixelsPerLabel'));
48e614ac 91 var ticks = [];
758a629f 92 var i, j, tickV, nTicks;
48e614ac 93 if (vals) {
758a629f 94 for (i = 0; i < vals.length; i++) {
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95 ticks.push({v: vals[i]});
96 }
97 } else {
98 // TODO(danvk): factor this log-scale block out into a separate function.
99 if (opts("logscale")) {
758a629f 100 nTicks = Math.floor(pixels / pixels_per_tick);
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101 var minIdx = Dygraph.binarySearch(a, Dygraph.PREFERRED_LOG_TICK_VALUES, 1);
102 var maxIdx = Dygraph.binarySearch(b, Dygraph.PREFERRED_LOG_TICK_VALUES, -1);
103 if (minIdx == -1) {
104 minIdx = 0;
105 }
106 if (maxIdx == -1) {
107 maxIdx = Dygraph.PREFERRED_LOG_TICK_VALUES.length - 1;
108 }
109 // Count the number of tick values would appear, if we can get at least
110 // nTicks / 4 accept them.
111 var lastDisplayed = null;
112 if (maxIdx - minIdx >= nTicks / 4) {
113 for (var idx = maxIdx; idx >= minIdx; idx--) {
114 var tickValue = Dygraph.PREFERRED_LOG_TICK_VALUES[idx];
115 var pixel_coord = Math.log(tickValue / a) / Math.log(b / a) * pixels;
116 var tick = { v: tickValue };
758a629f 117 if (lastDisplayed === null) {
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118 lastDisplayed = {
119 tickValue : tickValue,
120 pixel_coord : pixel_coord
121 };
122 } else {
123 if (Math.abs(pixel_coord - lastDisplayed.pixel_coord) >= pixels_per_tick) {
124 lastDisplayed = {
125 tickValue : tickValue,
126 pixel_coord : pixel_coord
127 };
128 } else {
129 tick.label = "";
130 }
131 }
132 ticks.push(tick);
133 }
134 // Since we went in backwards order.
135 ticks.reverse();
136 }
137 }
138
139 // ticks.length won't be 0 if the log scale function finds values to insert.
758a629f 140 if (ticks.length === 0) {
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141 // Basic idea:
142 // Try labels every 1, 2, 5, 10, 20, 50, 100, etc.
143 // Calculate the resulting tick spacing (i.e. this.height_ / nTicks).
144 // The first spacing greater than pixelsPerYLabel is what we use.
145 // TODO(danvk): version that works on a log scale.
146 var kmg2 = opts("labelsKMG2");
fa0d7ad8 147 var mults, base;
48e614ac 148 if (kmg2) {
48f5d762 149 mults = [1, 2, 4, 8, 16, 32, 64, 128, 256];
fa0d7ad8 150 base = 16;
48e614ac 151 } else {
48f5d762 152 mults = [1, 2, 5, 10, 20, 50, 100];
fa0d7ad8 153 base = 10;
48e614ac 154 }
fa0d7ad8 155
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156 // Get the maximum number of permitted ticks based on the
157 // graph's pixel size and pixels_per_tick setting.
158 var max_ticks = Math.ceil(pixels / pixels_per_tick);
159
160 // Now calculate the data unit equivalent of this tick spacing.
161 // Use abs() since graphs may have a reversed Y axis.
162 var units_per_tick = Math.abs(b - a) / max_ticks;
163
164 // Based on this, get a starting scale which is the largest
165 // integer power of the chosen base (10 or 16) that still remains
166 // below the requested pixels_per_tick spacing.
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167 var base_power = Math.floor(Math.log(units_per_tick) / Math.log(base));
168 var base_scale = Math.pow(base, base_power);
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169
170 // Now try multiples of the starting scale until we find one
171 // that results in tick marks spaced sufficiently far apart.
172 // The "mults" array should cover the range 1 .. base^2 to
173 // adjust for rounding and edge effects.
0cd1ad15 174 var scale, low_val, high_val, spacing;
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175 for (j = 0; j < mults.length; j++) {
176 scale = base_scale * mults[j];
177 low_val = Math.floor(a / scale) * scale;
178 high_val = Math.ceil(b / scale) * scale;
179 nTicks = Math.abs(high_val - low_val) / scale;
180 spacing = pixels / nTicks;
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181 if (spacing > pixels_per_tick) break;
182 }
183
184 // Construct the set of ticks.
185 // Allow reverse y-axis if it's explicitly requested.
186 if (low_val > high_val) scale *= -1;
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187 for (i = 0; i < nTicks; i++) {
188 tickV = low_val + i * scale;
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189 ticks.push( {v: tickV} );
190 }
191 }
192 }
193
d67a4279 194 var formatter = /**@type{AxisLabelFormatter}*/(opts('axisLabelFormatter'));
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195
196 // Add labels to the ticks.
758a629f 197 for (i = 0; i < ticks.length; i++) {
48e614ac 198 if (ticks[i].label !== undefined) continue; // Use current label.
48e614ac 199 // TODO(danvk): set granularity to something appropriate here.
2fd143d3 200 ticks[i].label = formatter(ticks[i].v, 0, opts, dygraph);
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201 }
202
203 return ticks;
204};
205
206
b2867ee1 207/** @type {Dygraph.Ticker} */
48e614ac 208Dygraph.dateTicker = function(a, b, pixels, opts, dygraph, vals) {
7a1f1877 209 var chosen = Dygraph.pickDateTickGranularity(a, b, pixels, opts);
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210
211 if (chosen >= 0) {
212 return Dygraph.getDateAxis(a, b, chosen, opts, dygraph);
213 } else {
214 // this can happen if self.width_ is zero.
215 return [];
216 }
217};
218
219// Time granularity enumeration
b2867ee1 220// TODO(danvk): make this an @enum
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221Dygraph.SECONDLY = 0;
222Dygraph.TWO_SECONDLY = 1;
223Dygraph.FIVE_SECONDLY = 2;
224Dygraph.TEN_SECONDLY = 3;
225Dygraph.THIRTY_SECONDLY = 4;
226Dygraph.MINUTELY = 5;
227Dygraph.TWO_MINUTELY = 6;
228Dygraph.FIVE_MINUTELY = 7;
229Dygraph.TEN_MINUTELY = 8;
230Dygraph.THIRTY_MINUTELY = 9;
231Dygraph.HOURLY = 10;
232Dygraph.TWO_HOURLY = 11;
233Dygraph.SIX_HOURLY = 12;
234Dygraph.DAILY = 13;
235Dygraph.WEEKLY = 14;
236Dygraph.MONTHLY = 15;
237Dygraph.QUARTERLY = 16;
238Dygraph.BIANNUAL = 17;
239Dygraph.ANNUAL = 18;
240Dygraph.DECADAL = 19;
241Dygraph.CENTENNIAL = 20;
242Dygraph.NUM_GRANULARITIES = 21;
243
b2867ee1 244/** @type {Array.<number>} */
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245Dygraph.SHORT_SPACINGS = [];
246Dygraph.SHORT_SPACINGS[Dygraph.SECONDLY] = 1000 * 1;
247Dygraph.SHORT_SPACINGS[Dygraph.TWO_SECONDLY] = 1000 * 2;
248Dygraph.SHORT_SPACINGS[Dygraph.FIVE_SECONDLY] = 1000 * 5;
249Dygraph.SHORT_SPACINGS[Dygraph.TEN_SECONDLY] = 1000 * 10;
250Dygraph.SHORT_SPACINGS[Dygraph.THIRTY_SECONDLY] = 1000 * 30;
251Dygraph.SHORT_SPACINGS[Dygraph.MINUTELY] = 1000 * 60;
252Dygraph.SHORT_SPACINGS[Dygraph.TWO_MINUTELY] = 1000 * 60 * 2;
253Dygraph.SHORT_SPACINGS[Dygraph.FIVE_MINUTELY] = 1000 * 60 * 5;
254Dygraph.SHORT_SPACINGS[Dygraph.TEN_MINUTELY] = 1000 * 60 * 10;
255Dygraph.SHORT_SPACINGS[Dygraph.THIRTY_MINUTELY] = 1000 * 60 * 30;
256Dygraph.SHORT_SPACINGS[Dygraph.HOURLY] = 1000 * 3600;
257Dygraph.SHORT_SPACINGS[Dygraph.TWO_HOURLY] = 1000 * 3600 * 2;
258Dygraph.SHORT_SPACINGS[Dygraph.SIX_HOURLY] = 1000 * 3600 * 6;
259Dygraph.SHORT_SPACINGS[Dygraph.DAILY] = 1000 * 86400;
260Dygraph.SHORT_SPACINGS[Dygraph.WEEKLY] = 1000 * 604800;
261
262/**
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263 * This is a list of human-friendly values at which to show tick marks on a log
264 * scale. It is k * 10^n, where k=1..9 and n=-39..+39, so:
265 * ..., 1, 2, 3, 4, 5, ..., 9, 10, 20, 30, ..., 90, 100, 200, 300, ...
266 * NOTE: this assumes that Dygraph.LOG_SCALE = 10.
b2867ee1 267 * @type {Array.<number>}
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268 */
269Dygraph.PREFERRED_LOG_TICK_VALUES = function() {
270 var vals = [];
271 for (var power = -39; power <= 39; power++) {
272 var range = Math.pow(10, power);
273 for (var mult = 1; mult <= 9; mult++) {
274 var val = range * mult;
275 vals.push(val);
276 }
277 }
278 return vals;
279}();
280
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281/**
282 * Determine the correct granularity of ticks on a date axis.
283 *
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284 * @param {number} a Left edge of the chart (ms)
285 * @param {number} b Right edge of the chart (ms)
286 * @param {number} pixels Size of the chart in the relevant dimension (width).
287 * @param {function(string):*} opts Function mapping from option name ->
288 * value.
289 * @return {number} The appropriate axis granularity for this chart. See the
290 * enumeration of possible values in dygraph-tickers.js.
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291 */
292Dygraph.pickDateTickGranularity = function(a, b, pixels, opts) {
b2867ee1 293 var pixels_per_tick = /** @type{number} */(opts('pixelsPerLabel'));
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294 for (var i = 0; i < Dygraph.NUM_GRANULARITIES; i++) {
295 var num_ticks = Dygraph.numDateTicks(a, b, i);
296 if (pixels / num_ticks >= pixels_per_tick) {
297 return i;
298 }
299 }
300 return -1;
301};
302
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303/**
304 * @param {number} start_time
305 * @param {number} end_time
306 * @param {number} granularity (one of the granularities enumerated above)
307 * @return {number} Number of ticks that would result.
308 */
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309Dygraph.numDateTicks = function(start_time, end_time, granularity) {
310 if (granularity < Dygraph.MONTHLY) {
311 // Generate one tick mark for every fixed interval of time.
312 var spacing = Dygraph.SHORT_SPACINGS[granularity];
313 return Math.floor(0.5 + 1.0 * (end_time - start_time) / spacing);
314 } else {
315 var year_mod = 1; // e.g. to only print one point every 10 years.
316 var num_months = 12;
317 if (granularity == Dygraph.QUARTERLY) num_months = 3;
318 if (granularity == Dygraph.BIANNUAL) num_months = 2;
319 if (granularity == Dygraph.ANNUAL) num_months = 1;
320 if (granularity == Dygraph.DECADAL) { num_months = 1; year_mod = 10; }
321 if (granularity == Dygraph.CENTENNIAL) { num_months = 1; year_mod = 100; }
322
323 var msInYear = 365.2524 * 24 * 3600 * 1000;
324 var num_years = 1.0 * (end_time - start_time) / msInYear;
325 return Math.floor(0.5 + 1.0 * num_years * num_months / year_mod);
326 }
327};
328
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329/**
330 * @param {number} start_time
331 * @param {number} end_time
332 * @param {number} granularity (one of the granularities enumerated above)
333 * @param {function(string):*} opts Function mapping from option name -&gt; value.
334 * @param {Dygraph=} dg
335 * @return {!Dygraph.TickList}
336 */
48e614ac 337Dygraph.getDateAxis = function(start_time, end_time, granularity, opts, dg) {
d67a4279 338 var formatter = /** @type{AxisLabelFormatter} */(
b2867ee1 339 opts("axisLabelFormatter"));
48e614ac 340 var ticks = [];
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341 var t;
342
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343 if (granularity < Dygraph.MONTHLY) {
344 // Generate one tick mark for every fixed interval of time.
345 var spacing = Dygraph.SHORT_SPACINGS[granularity];
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346
347 // Find a time less than start_time which occurs on a "nice" time boundary
348 // for this granularity.
349 var g = spacing / 1000;
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350 var d = new Date(start_time);
351 d.setMilliseconds(0);
758a629f 352 var x;
48e614ac 353 if (g <= 60) { // seconds
758a629f 354 x = d.getSeconds(); d.setSeconds(x - x % g);
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355 } else {
356 d.setSeconds(0);
357 g /= 60;
358 if (g <= 60) { // minutes
758a629f 359 x = d.getMinutes(); d.setMinutes(x - x % g);
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360 } else {
361 d.setMinutes(0);
362 g /= 60;
363
364 if (g <= 24) { // days
758a629f 365 x = d.getHours(); d.setHours(x - x % g);
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366 } else {
367 d.setHours(0);
368 g /= 24;
369
370 if (g == 7) { // one week
371 d.setDate(d.getDate() - d.getDay());
372 }
373 }
374 }
375 }
376 start_time = d.getTime();
377
c6975231 378 var start_offset_min = new Date(start_time).getTimezoneOffset();
758a629f 379 for (t = start_time; t <= end_time; t += spacing) {
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380 var d = new Date(t);
381
382 // This ensures that we stay on the same hourly "rhythm" across
383 // daylight savings transitions. Without this, the ticks could get off
384 // by an hour. See tests/daylight-savings.html or issue 147.
385 if (d.getTimezoneOffset() != start_offset_min) {
386 t += (d.getTimezoneOffset() - start_offset_min) * 60 * 1000;
387 d = new Date(t);
388 start_offset_min = d.getTimezoneOffset();
389 }
390
48e614ac 391 ticks.push({ v:t,
c6975231 392 label: formatter(d, granularity, opts, dg)
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393 });
394 }
395 } else {
396 // Display a tick mark on the first of a set of months of each year.
397 // Years get a tick mark iff y % year_mod == 0. This is useful for
398 // displaying a tick mark once every 10 years, say, on long time scales.
399 var months;
400 var year_mod = 1; // e.g. to only print one point every 10 years.
401
402 if (granularity == Dygraph.MONTHLY) {
ccd9d7c2 403 months = [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 ];
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404 } else if (granularity == Dygraph.QUARTERLY) {
405 months = [ 0, 3, 6, 9 ];
406 } else if (granularity == Dygraph.BIANNUAL) {
407 months = [ 0, 6 ];
408 } else if (granularity == Dygraph.ANNUAL) {
409 months = [ 0 ];
410 } else if (granularity == Dygraph.DECADAL) {
411 months = [ 0 ];
412 year_mod = 10;
413 } else if (granularity == Dygraph.CENTENNIAL) {
414 months = [ 0 ];
415 year_mod = 100;
416 } else {
417 Dygraph.warn("Span of dates is too long");
418 }
419
420 var start_year = new Date(start_time).getFullYear();
421 var end_year = new Date(end_time).getFullYear();
422 var zeropad = Dygraph.zeropad;
423 for (var i = start_year; i <= end_year; i++) {
758a629f 424 if (i % year_mod !== 0) continue;
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425 for (var j = 0; j < months.length; j++) {
426 var date_str = i + "/" + zeropad(1 + months[j]) + "/01";
758a629f 427 t = Dygraph.dateStrToMillis(date_str);
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428 if (t < start_time || t > end_time) continue;
429 ticks.push({ v:t,
430 label: formatter(new Date(t), granularity, opts, dg)
431 });
432 }
433 }
434 }
435
436 return ticks;
437};
438
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439// These are set here so that this file can be included after dygraph.js
440// or independently.
441Dygraph.DEFAULT_ATTRS = Dygraph.DEFAULT_ATTRS || {};
442Dygraph.DEFAULT_ATTRS['axes'] = Dygraph.DEFAULT_ATTRS['axes'] || {};
443Dygraph.DEFAULT_ATTRS['axes']['x'] = Dygraph.DEFAULT_ATTRS['axes']['x'] || {};
444Dygraph.DEFAULT_ATTRS['axes']['y'] = Dygraph.DEFAULT_ATTRS['axes']['y'] || {};
445Dygraph.DEFAULT_ATTRS['axes']['y2'] = Dygraph.DEFAULT_ATTRS['axes']['y2'] || {};
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446Dygraph.DEFAULT_ATTRS['axes']['x']['ticker'] = Dygraph.dateTicker;
447Dygraph.DEFAULT_ATTRS['axes']['y']['ticker'] = Dygraph.numericTicks;
448Dygraph.DEFAULT_ATTRS['axes']['y2']['ticker'] = Dygraph.numericTicks;