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[dygraphs.git] / src / dygraph-tickers.js
1 /**
2 * @license
3 * Copyright 2011 Dan Vanderkam (danvdk@gmail.com)
4 * MIT-licensed (http://opensource.org/licenses/MIT)
5 */
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
61 /*jshint sub:true */
62 /*global Dygraph:false */
63 "use strict";
64
65 import * as utils from './dygraph-utils';
66
67 /** @typedef {Array.<{v:number, label:string, label_v:(string|undefined)}>} */
68 var TickList = undefined; // the ' = undefined' keeps jshint happy.
69
70 /** @typedef {function(
71 * number,
72 * number,
73 * number,
74 * function(string):*,
75 * Dygraph=,
76 * Array.<number>=
77 * ): TickList}
78 */
79 var Ticker = undefined; // the ' = undefined' keeps jshint happy.
80
81 /** @type {Ticker} */
82 export var numericLinearTicks = function(a, b, pixels, opts, dygraph, vals) {
83 var nonLogscaleOpts = function(opt) {
84 if (opt === 'logscale') return false;
85 return opts(opt);
86 };
87 return numericTicks(a, b, pixels, nonLogscaleOpts, dygraph, vals);
88 };
89
90 /** @type {Ticker} */
91 export var numericTicks = function(a, b, pixels, opts, dygraph, vals) {
92 var pixels_per_tick = /** @type{number} */(opts('pixelsPerLabel'));
93 var ticks = [];
94 var i, j, tickV, nTicks;
95 if (vals) {
96 for (i = 0; i < vals.length; i++) {
97 ticks.push({v: vals[i]});
98 }
99 } else {
100 // TODO(danvk): factor this log-scale block out into a separate function.
101 if (opts("logscale")) {
102 nTicks = Math.floor(pixels / pixels_per_tick);
103 var minIdx = utils.binarySearch(a, PREFERRED_LOG_TICK_VALUES, 1);
104 var maxIdx = utils.binarySearch(b, PREFERRED_LOG_TICK_VALUES, -1);
105 if (minIdx == -1) {
106 minIdx = 0;
107 }
108 if (maxIdx == -1) {
109 maxIdx = PREFERRED_LOG_TICK_VALUES.length - 1;
110 }
111 // Count the number of tick values would appear, if we can get at least
112 // nTicks / 4 accept them.
113 var lastDisplayed = null;
114 if (maxIdx - minIdx >= nTicks / 4) {
115 for (var idx = maxIdx; idx >= minIdx; idx--) {
116 var tickValue = PREFERRED_LOG_TICK_VALUES[idx];
117 var pixel_coord = Math.log(tickValue / a) / Math.log(b / a) * pixels;
118 var tick = { v: tickValue };
119 if (lastDisplayed === null) {
120 lastDisplayed = {
121 tickValue : tickValue,
122 pixel_coord : pixel_coord
123 };
124 } else {
125 if (Math.abs(pixel_coord - lastDisplayed.pixel_coord) >= pixels_per_tick) {
126 lastDisplayed = {
127 tickValue : tickValue,
128 pixel_coord : pixel_coord
129 };
130 } else {
131 tick.label = "";
132 }
133 }
134 ticks.push(tick);
135 }
136 // Since we went in backwards order.
137 ticks.reverse();
138 }
139 }
140
141 // ticks.length won't be 0 if the log scale function finds values to insert.
142 if (ticks.length === 0) {
143 // Basic idea:
144 // Try labels every 1, 2, 5, 10, 20, 50, 100, etc.
145 // Calculate the resulting tick spacing (i.e. this.height_ / nTicks).
146 // The first spacing greater than pixelsPerYLabel is what we use.
147 // TODO(danvk): version that works on a log scale.
148 var kmg2 = opts("labelsKMG2");
149 var mults, base;
150 if (kmg2) {
151 mults = [1, 2, 4, 8, 16, 32, 64, 128, 256];
152 base = 16;
153 } else {
154 mults = [1, 2, 5, 10, 20, 50, 100];
155 base = 10;
156 }
157
158 // Get the maximum number of permitted ticks based on the
159 // graph's pixel size and pixels_per_tick setting.
160 var max_ticks = Math.ceil(pixels / pixels_per_tick);
161
162 // Now calculate the data unit equivalent of this tick spacing.
163 // Use abs() since graphs may have a reversed Y axis.
164 var units_per_tick = Math.abs(b - a) / max_ticks;
165
166 // Based on this, get a starting scale which is the largest
167 // integer power of the chosen base (10 or 16) that still remains
168 // below the requested pixels_per_tick spacing.
169 var base_power = Math.floor(Math.log(units_per_tick) / Math.log(base));
170 var base_scale = Math.pow(base, base_power);
171
172 // Now try multiples of the starting scale until we find one
173 // that results in tick marks spaced sufficiently far apart.
174 // The "mults" array should cover the range 1 .. base^2 to
175 // adjust for rounding and edge effects.
176 var scale, low_val, high_val, spacing;
177 for (j = 0; j < mults.length; j++) {
178 scale = base_scale * mults[j];
179 low_val = Math.floor(a / scale) * scale;
180 high_val = Math.ceil(b / scale) * scale;
181 nTicks = Math.abs(high_val - low_val) / scale;
182 spacing = pixels / nTicks;
183 if (spacing > pixels_per_tick) break;
184 }
185
186 // Construct the set of ticks.
187 // Allow reverse y-axis if it's explicitly requested.
188 if (low_val > high_val) scale *= -1;
189 for (i = 0; i <= nTicks; i++) {
190 tickV = low_val + i * scale;
191 ticks.push( {v: tickV} );
192 }
193 }
194 }
195
196 var formatter = /**@type{AxisLabelFormatter}*/(opts('axisLabelFormatter'));
197
198 // Add labels to the ticks.
199 for (i = 0; i < ticks.length; i++) {
200 if (ticks[i].label !== undefined) continue; // Use current label.
201 // TODO(danvk): set granularity to something appropriate here.
202 ticks[i].label = formatter.call(dygraph, ticks[i].v, 0, opts, dygraph);
203 }
204
205 return ticks;
206 };
207
208
209 /** @type {Ticker} */
210 export var dateTicker = function(a, b, pixels, opts, dygraph, vals) {
211 var chosen = pickDateTickGranularity(a, b, pixels, opts);
212
213 if (chosen >= 0) {
214 return getDateAxis(a, b, chosen, opts, dygraph);
215 } else {
216 // this can happen if self.width_ is zero.
217 return [];
218 }
219 };
220
221 // Time granularity enumeration
222 export var Granularity = {
223 SECONDLY: 0,
224 TWO_SECONDLY: 1,
225 FIVE_SECONDLY: 2,
226 TEN_SECONDLY: 3,
227 THIRTY_SECONDLY : 4,
228 MINUTELY: 5,
229 TWO_MINUTELY: 6,
230 FIVE_MINUTELY: 7,
231 TEN_MINUTELY: 8,
232 THIRTY_MINUTELY: 9,
233 HOURLY: 10,
234 TWO_HOURLY: 11,
235 SIX_HOURLY: 12,
236 DAILY: 13,
237 TWO_DAILY: 14,
238 WEEKLY: 15,
239 MONTHLY: 16,
240 QUARTERLY: 17,
241 BIANNUAL: 18,
242 ANNUAL: 19,
243 DECADAL: 20,
244 CENTENNIAL: 21,
245 NUM_GRANULARITIES: 22
246 }
247
248 // Date components enumeration (in the order of the arguments in Date)
249 // TODO: make this an @enum
250 var DateField = {
251 DATEFIELD_Y: 0,
252 DATEFIELD_M: 1,
253 DATEFIELD_D: 2,
254 DATEFIELD_HH: 3,
255 DATEFIELD_MM: 4,
256 DATEFIELD_SS: 5,
257 DATEFIELD_MS: 6,
258 NUM_DATEFIELDS: 7
259 };
260
261
262 /**
263 * The value of datefield will start at an even multiple of "step", i.e.
264 * if datefield=SS and step=5 then the first tick will be on a multiple of 5s.
265 *
266 * For granularities <= HOURLY, ticks are generated every `spacing` ms.
267 *
268 * At coarser granularities, ticks are generated by incrementing `datefield` by
269 * `step`. In this case, the `spacing` value is only used to estimate the
270 * number of ticks. It should roughly correspond to the spacing between
271 * adjacent ticks.
272 *
273 * @type {Array.<{datefield:number, step:number, spacing:number}>}
274 */
275 var TICK_PLACEMENT = [];
276 TICK_PLACEMENT[Granularity.SECONDLY] = {datefield: DateField.DATEFIELD_SS, step: 1, spacing: 1000 * 1};
277 TICK_PLACEMENT[Granularity.TWO_SECONDLY] = {datefield: DateField.DATEFIELD_SS, step: 2, spacing: 1000 * 2};
278 TICK_PLACEMENT[Granularity.FIVE_SECONDLY] = {datefield: DateField.DATEFIELD_SS, step: 5, spacing: 1000 * 5};
279 TICK_PLACEMENT[Granularity.TEN_SECONDLY] = {datefield: DateField.DATEFIELD_SS, step: 10, spacing: 1000 * 10};
280 TICK_PLACEMENT[Granularity.THIRTY_SECONDLY] = {datefield: DateField.DATEFIELD_SS, step: 30, spacing: 1000 * 30};
281 TICK_PLACEMENT[Granularity.MINUTELY] = {datefield: DateField.DATEFIELD_MM, step: 1, spacing: 1000 * 60};
282 TICK_PLACEMENT[Granularity.TWO_MINUTELY] = {datefield: DateField.DATEFIELD_MM, step: 2, spacing: 1000 * 60 * 2};
283 TICK_PLACEMENT[Granularity.FIVE_MINUTELY] = {datefield: DateField.DATEFIELD_MM, step: 5, spacing: 1000 * 60 * 5};
284 TICK_PLACEMENT[Granularity.TEN_MINUTELY] = {datefield: DateField.DATEFIELD_MM, step: 10, spacing: 1000 * 60 * 10};
285 TICK_PLACEMENT[Granularity.THIRTY_MINUTELY] = {datefield: DateField.DATEFIELD_MM, step: 30, spacing: 1000 * 60 * 30};
286 TICK_PLACEMENT[Granularity.HOURLY] = {datefield: DateField.DATEFIELD_HH, step: 1, spacing: 1000 * 3600};
287 TICK_PLACEMENT[Granularity.TWO_HOURLY] = {datefield: DateField.DATEFIELD_HH, step: 2, spacing: 1000 * 3600 * 2};
288 TICK_PLACEMENT[Granularity.SIX_HOURLY] = {datefield: DateField.DATEFIELD_HH, step: 6, spacing: 1000 * 3600 * 6};
289 TICK_PLACEMENT[Granularity.DAILY] = {datefield: DateField.DATEFIELD_D, step: 1, spacing: 1000 * 86400};
290 TICK_PLACEMENT[Granularity.TWO_DAILY] = {datefield: DateField.DATEFIELD_D, step: 2, spacing: 1000 * 86400 * 2};
291 TICK_PLACEMENT[Granularity.WEEKLY] = {datefield: DateField.DATEFIELD_D, step: 7, spacing: 1000 * 604800};
292 TICK_PLACEMENT[Granularity.MONTHLY] = {datefield: DateField.DATEFIELD_M, step: 1, spacing: 1000 * 7200 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 / 12
293 TICK_PLACEMENT[Granularity.QUARTERLY] = {datefield: DateField.DATEFIELD_M, step: 3, spacing: 1000 * 21600 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 / 4
294 TICK_PLACEMENT[Granularity.BIANNUAL] = {datefield: DateField.DATEFIELD_M, step: 6, spacing: 1000 * 43200 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 / 2
295 TICK_PLACEMENT[Granularity.ANNUAL] = {datefield: DateField.DATEFIELD_Y, step: 1, spacing: 1000 * 86400 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 * 1
296 TICK_PLACEMENT[Granularity.DECADAL] = {datefield: DateField.DATEFIELD_Y, step: 10, spacing: 1000 * 864000 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 * 10
297 TICK_PLACEMENT[Granularity.CENTENNIAL] = {datefield: DateField.DATEFIELD_Y, step: 100, spacing: 1000 * 8640000 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 * 100
298
299
300 /**
301 * This is a list of human-friendly values at which to show tick marks on a log
302 * scale. It is k * 10^n, where k=1..9 and n=-39..+39, so:
303 * ..., 1, 2, 3, 4, 5, ..., 9, 10, 20, 30, ..., 90, 100, 200, 300, ...
304 * NOTE: this assumes that utils.LOG_SCALE = 10.
305 * @type {Array.<number>}
306 */
307 var PREFERRED_LOG_TICK_VALUES = (function() {
308 var vals = [];
309 for (var power = -39; power <= 39; power++) {
310 var range = Math.pow(10, power);
311 for (var mult = 1; mult <= 9; mult++) {
312 var val = range * mult;
313 vals.push(val);
314 }
315 }
316 return vals;
317 })();
318
319 /**
320 * Determine the correct granularity of ticks on a date axis.
321 *
322 * @param {number} a Left edge of the chart (ms)
323 * @param {number} b Right edge of the chart (ms)
324 * @param {number} pixels Size of the chart in the relevant dimension (width).
325 * @param {function(string):*} opts Function mapping from option name -&gt; value.
326 * @return {number} The appropriate axis granularity for this chart. See the
327 * enumeration of possible values in dygraph-tickers.js.
328 */
329 var pickDateTickGranularity = function(a, b, pixels, opts) {
330 var pixels_per_tick = /** @type{number} */(opts('pixelsPerLabel'));
331 for (var i = 0; i < Granularity.NUM_GRANULARITIES; i++) {
332 var num_ticks = numDateTicks(a, b, i);
333 if (pixels / num_ticks >= pixels_per_tick) {
334 return i;
335 }
336 }
337 return -1;
338 };
339
340 /**
341 * Compute the number of ticks on a date axis for a given granularity.
342 * @param {number} start_time
343 * @param {number} end_time
344 * @param {number} granularity (one of the granularities enumerated above)
345 * @return {number} (Approximate) number of ticks that would result.
346 */
347 var numDateTicks = function(start_time, end_time, granularity) {
348 var spacing = TICK_PLACEMENT[granularity].spacing;
349 return Math.round(1.0 * (end_time - start_time) / spacing);
350 };
351
352 /**
353 * Compute the positions and labels of ticks on a date axis for a given granularity.
354 * @param {number} start_time
355 * @param {number} end_time
356 * @param {number} granularity (one of the granularities enumerated above)
357 * @param {function(string):*} opts Function mapping from option name -&gt; value.
358 * @param {Dygraph=} dg
359 * @return {!TickList}
360 */
361 export var getDateAxis = function(start_time, end_time, granularity, opts, dg) {
362 var formatter = /** @type{AxisLabelFormatter} */(
363 opts("axisLabelFormatter"));
364 var utc = opts("labelsUTC");
365 var accessors = utc ? utils.DateAccessorsUTC : utils.DateAccessorsLocal;
366
367 var datefield = TICK_PLACEMENT[granularity].datefield;
368 var step = TICK_PLACEMENT[granularity].step;
369 var spacing = TICK_PLACEMENT[granularity].spacing;
370
371 // Choose a nice tick position before the initial instant.
372 // Currently, this code deals properly with the existent daily granularities:
373 // DAILY (with step of 1) and WEEKLY (with step of 7 but specially handled).
374 // Other daily granularities (say TWO_DAILY) should also be handled specially
375 // by setting the start_date_offset to 0.
376 var start_date = new Date(start_time);
377 var date_array = [];
378 date_array[DateField.DATEFIELD_Y] = accessors.getFullYear(start_date);
379 date_array[DateField.DATEFIELD_M] = accessors.getMonth(start_date);
380 date_array[DateField.DATEFIELD_D] = accessors.getDate(start_date);
381 date_array[DateField.DATEFIELD_HH] = accessors.getHours(start_date);
382 date_array[DateField.DATEFIELD_MM] = accessors.getMinutes(start_date);
383 date_array[DateField.DATEFIELD_SS] = accessors.getSeconds(start_date);
384 date_array[DateField.DATEFIELD_MS] = accessors.getMilliseconds(start_date);
385
386 var start_date_offset = date_array[datefield] % step;
387 if (granularity == Granularity.WEEKLY) {
388 // This will put the ticks on Sundays.
389 start_date_offset = accessors.getDay(start_date);
390 }
391
392 date_array[datefield] -= start_date_offset;
393 for (var df = datefield + 1; df < DateField.NUM_DATEFIELDS; df++) {
394 // The minimum value is 1 for the day of month, and 0 for all other fields.
395 date_array[df] = (df === DateField.DATEFIELD_D) ? 1 : 0;
396 }
397
398 // Generate the ticks.
399 // For granularities not coarser than HOURLY we use the fact that:
400 // the number of milliseconds between ticks is constant
401 // and equal to the defined spacing.
402 // Otherwise we rely on the 'roll over' property of the Date functions:
403 // when some date field is set to a value outside of its logical range,
404 // the excess 'rolls over' the next (more significant) field.
405 // However, when using local time with DST transitions,
406 // there are dates that do not represent any time value at all
407 // (those in the hour skipped at the 'spring forward'),
408 // and the JavaScript engines usually return an equivalent value.
409 // Hence we have to check that the date is properly increased at each step,
410 // returning a date at a nice tick position.
411 var ticks = [];
412 var tick_date = accessors.makeDate.apply(null, date_array);
413 var tick_time = tick_date.getTime();
414 if (granularity <= Granularity.HOURLY) {
415 if (tick_time < start_time) {
416 tick_time += spacing;
417 tick_date = new Date(tick_time);
418 }
419 while (tick_time <= end_time) {
420 ticks.push({ v: tick_time,
421 label: formatter.call(dg, tick_date, granularity, opts, dg)
422 });
423 tick_time += spacing;
424 tick_date = new Date(tick_time);
425 }
426 } else {
427 if (tick_time < start_time) {
428 date_array[datefield] += step;
429 tick_date = accessors.makeDate.apply(null, date_array);
430 tick_time = tick_date.getTime();
431 }
432 while (tick_time <= end_time) {
433 if (granularity >= Granularity.DAILY ||
434 accessors.getHours(tick_date) % step === 0) {
435 ticks.push({ v: tick_time,
436 label: formatter.call(dg, tick_date, granularity, opts, dg)
437 });
438 }
439 date_array[datefield] += step;
440 tick_date = accessors.makeDate.apply(null, date_array);
441 tick_time = tick_date.getTime();
442 }
443 }
444 return ticks;
445 };
446
447 // These are set here so that this file can be included after dygraph.js
448 // or independently.
449 // if (Dygraph &&
450 // Dygraph.DEFAULT_ATTRS &&
451 // Dygraph.DEFAULT_ATTRS['axes'] &&
452 // Dygraph.DEFAULT_ATTRS['axes']['x'] &&
453 // Dygraph.DEFAULT_ATTRS['axes']['y'] &&
454 // Dygraph.DEFAULT_ATTRS['axes']['y2']) {
455 // Dygraph.DEFAULT_ATTRS['axes']['x']['ticker'] = Dygraph.dateTicker;
456 // Dygraph.DEFAULT_ATTRS['axes']['y']['ticker'] = Dygraph.numericTicks;
457 // Dygraph.DEFAULT_ATTRS['axes']['y2']['ticker'] = Dygraph.numericTicks;
458 // }