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 globalstrict:true, sub:true */
  62 /*global Dygraph:false */
  63 "use strict";
  64
  65 /** @typedef {Array.<{v:number, label:string, label_v:(string|undefined)}>} */
  66 Dygraph.TickList = undefined;  // the ' = undefined' keeps jshint happy.
  67
  68 /** @typedef {function(
  69  *    number,
  70  *    number,
  71  *    number,
  72  *    function(string):*,
  73  *    Dygraph=,
  74  *    Array.<number>=
  75  *  ): Dygraph.TickList}
  76  */
  77 Dygraph.Ticker = undefined;  // the ' = undefined' keeps jshint happy.
  78
  79 /** @type {Dygraph.Ticker} */
  80 Dygraph.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
  88 /** @type {Dygraph.Ticker} */
  89 Dygraph.numericTicks = function(a, b, pixels, opts, dygraph, vals) {
  90   var pixels_per_tick = /** @type{number} */(opts('pixelsPerLabel'));
  91   var ticks = [];
  92   var i, j, tickV, nTicks;
  93   if (vals) {
  94     for (i = 0; i < vals.length; i++) {
  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")) {
 100       nTicks  = Math.floor(pixels / pixels_per_tick);
 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 };
 117           if (lastDisplayed === null) {
 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.
 140     if (ticks.length === 0) {
 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");
 147       var mults, base;
 148       if (kmg2) {
 149         mults = [1, 2, 4, 8, 16, 32, 64, 128, 256];
 150         base = 16;
 151       } else {
 152         mults = [1, 2, 5, 10, 20, 50, 100];
 153         base = 10;
 154       }
 155
 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.
 167       var base_power = Math.floor(Math.log(units_per_tick) / Math.log(base));
 168       var base_scale = Math.pow(base, base_power);
 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.
 174       var scale, low_val, high_val, spacing;
 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;
 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;
 187       for (i = 0; i <= nTicks; i++) {
 188         tickV = low_val + i * scale;
 189         ticks.push( {v: tickV} );
 190       }
 191     }
 192   }
 193
 194   var formatter = /**@type{AxisLabelFormatter}*/(opts('axisLabelFormatter'));
 195
 196   // Add labels to the ticks.
 197   for (i = 0; i < ticks.length; i++) {
 198     if (ticks[i].label !== undefined) continue;  // Use current label.
 199     // TODO(danvk): set granularity to something appropriate here.
 200     ticks[i].label = formatter(ticks[i].v, 0, opts, dygraph);
 201   }
 202
 203   return ticks;
 204 };
 205
 206
 207 /** @type {Dygraph.Ticker} */
 208 Dygraph.dateTicker = function(a, b, pixels, opts, dygraph, vals) {
 209   var chosen = Dygraph.pickDateTickGranularity(a, b, pixels, opts);
 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
 220 // TODO(danvk): make this an @enum
 221 Dygraph.SECONDLY = 0;
 222 Dygraph.TWO_SECONDLY = 1;
 223 Dygraph.FIVE_SECONDLY = 2;
 224 Dygraph.TEN_SECONDLY = 3;
 225 Dygraph.THIRTY_SECONDLY  = 4;
 226 Dygraph.MINUTELY = 5;
 227 Dygraph.TWO_MINUTELY = 6;
 228 Dygraph.FIVE_MINUTELY = 7;
 229 Dygraph.TEN_MINUTELY = 8;
 230 Dygraph.THIRTY_MINUTELY = 9;
 231 Dygraph.HOURLY = 10;
 232 Dygraph.TWO_HOURLY = 11;
 233 Dygraph.SIX_HOURLY = 12;
 234 Dygraph.DAILY = 13;
 235 Dygraph.WEEKLY = 14;
 236 Dygraph.MONTHLY = 15;
 237 Dygraph.QUARTERLY = 16;
 238 Dygraph.BIANNUAL = 17;
 239 Dygraph.ANNUAL = 18;
 240 Dygraph.DECADAL = 19;
 241 Dygraph.CENTENNIAL = 20;
 242 Dygraph.NUM_GRANULARITIES = 21;
 243
 244 /** @type {Array.<number>} */
 245 Dygraph.SHORT_SPACINGS = [];
 246 Dygraph.SHORT_SPACINGS[Dygraph.SECONDLY]        = 1000 * 1;
 247 Dygraph.SHORT_SPACINGS[Dygraph.TWO_SECONDLY]    = 1000 * 2;
 248 Dygraph.SHORT_SPACINGS[Dygraph.FIVE_SECONDLY]   = 1000 * 5;
 249 Dygraph.SHORT_SPACINGS[Dygraph.TEN_SECONDLY]    = 1000 * 10;
 250 Dygraph.SHORT_SPACINGS[Dygraph.THIRTY_SECONDLY] = 1000 * 30;
 251 Dygraph.SHORT_SPACINGS[Dygraph.MINUTELY]        = 1000 * 60;
 252 Dygraph.SHORT_SPACINGS[Dygraph.TWO_MINUTELY]    = 1000 * 60 * 2;
 253 Dygraph.SHORT_SPACINGS[Dygraph.FIVE_MINUTELY]   = 1000 * 60 * 5;
 254 Dygraph.SHORT_SPACINGS[Dygraph.TEN_MINUTELY]    = 1000 * 60 * 10;
 255 Dygraph.SHORT_SPACINGS[Dygraph.THIRTY_MINUTELY] = 1000 * 60 * 30;
 256 Dygraph.SHORT_SPACINGS[Dygraph.HOURLY]          = 1000 * 3600;
 257 Dygraph.SHORT_SPACINGS[Dygraph.TWO_HOURLY]      = 1000 * 3600 * 2;
 258 Dygraph.SHORT_SPACINGS[Dygraph.SIX_HOURLY]      = 1000 * 3600 * 6;
 259 Dygraph.SHORT_SPACINGS[Dygraph.DAILY]           = 1000 * 86400;
 260 Dygraph.SHORT_SPACINGS[Dygraph.WEEKLY]          = 1000 * 604800;
 261
 262 /**
 263  * A collection of objects specifying where it is acceptable to place tick
 264  * marks for granularities larger than WEEKLY.
 265  * 'months' is an array of month indexes on which to place tick marks.
 266  * 'year_mod' ticks are placed when year % year_mod = 0.
 267  * @type {Array.<Object>}
 268  */
 269 Dygraph.LONG_TICK_PLACEMENTS = [];
 270 Dygraph.LONG_TICK_PLACEMENTS[Dygraph.MONTHLY] = {
 271   months : [0,1,2,3,4,5,6,7,8,9,10,11],
 272   year_mod : 1
 273 };
 274 Dygraph.LONG_TICK_PLACEMENTS[Dygraph.QUARTERLY] = {
 275   months: [0,3,6,9],
 276   year_mod: 1
 277 };
 278 Dygraph.LONG_TICK_PLACEMENTS[Dygraph.BIANNUAL] = {
 279   months: [0,6],
 280   year_mod: 1
 281 };
 282 Dygraph.LONG_TICK_PLACEMENTS[Dygraph.ANNUAL] = {
 283   months: [0],
 284   year_mod: 1
 285 };
 286 Dygraph.LONG_TICK_PLACEMENTS[Dygraph.DECADAL] = {
 287   months: [0],
 288   year_mod: 10
 289 };
 290 Dygraph.LONG_TICK_PLACEMENTS[Dygraph.CENTENNIAL] = {
 291   months: [0],
 292   year_mod: 100
 293 };
 294
 295 /**
 296  * This is a list of human-friendly values at which to show tick marks on a log
 297  * scale. It is k * 10^n, where k=1..9 and n=-39..+39, so:
 298  * ..., 1, 2, 3, 4, 5, ..., 9, 10, 20, 30, ..., 90, 100, 200, 300, ...
 299  * NOTE: this assumes that Dygraph.LOG_SCALE = 10.
 300  * @type {Array.<number>}
 301  */
 302 Dygraph.PREFERRED_LOG_TICK_VALUES = function() {
 303   var vals = [];
 304   for (var power = -39; power <= 39; power++) {
 305     var range = Math.pow(10, power);
 306     for (var mult = 1; mult <= 9; mult++) {
 307       var val = range * mult;
 308       vals.push(val);
 309     }
 310   }
 311   return vals;
 312 }();
 313
 314 /**
 315  * Determine the correct granularity of ticks on a date axis.
 316  *
 317  * @param {number} a Left edge of the chart (ms)
 318  * @param {number} b Right edge of the chart (ms)
 319  * @param {number} pixels Size of the chart in the relevant dimension (width).
 320  * @param {function(string):*} opts Function mapping from option name ->
 321  *     value.
 322  * @return {number} The appropriate axis granularity for this chart. See the
 323  *     enumeration of possible values in dygraph-tickers.js.
 324  */
 325 Dygraph.pickDateTickGranularity = function(a, b, pixels, opts) {
 326   var pixels_per_tick = /** @type{number} */(opts('pixelsPerLabel'));
 327   for (var i = 0; i < Dygraph.NUM_GRANULARITIES; i++) {
 328     var num_ticks = Dygraph.numDateTicks(a, b, i);
 329     if (pixels / num_ticks >= pixels_per_tick) {
 330       return i;
 331     }
 332   }
 333   return -1;
 334 };
 335
 336 /**
 337  * @param {number} start_time
 338  * @param {number} end_time
 339  * @param {number} granularity (one of the granularities enumerated above)
 340  * @return {number} Number of ticks that would result.
 341  */
 342 Dygraph.numDateTicks = function(start_time, end_time, granularity) {
 343   if (granularity < Dygraph.MONTHLY) {
 344     // Generate one tick mark for every fixed interval of time.
 345     var spacing = Dygraph.SHORT_SPACINGS[granularity];
 346     return Math.floor(0.5 + 1.0 * (end_time - start_time) / spacing);
 347   } else {
 348     var tickPlacement = Dygraph.LONG_TICK_PLACEMENTS[granularity];
 349
 350     var msInYear = 365.2524 * 24 * 3600 * 1000;
 351     var num_years = 1.0 * (end_time - start_time) / msInYear;
 352     return Math.floor(0.5 + 1.0 * num_years * tickPlacement.months.length / tickPlacement.year_mod);
 353   }
 354 };
 355
 356 /**
 357  * @param {number} start_time
 358  * @param {number} end_time
 359  * @param {number} granularity (one of the granularities enumerated above)
 360  * @param {function(string):*} opts Function mapping from option name -&gt; value.
 361  * @param {Dygraph=} dg
 362  * @return {!Dygraph.TickList}
 363  */
 364 Dygraph.getDateAxis = function(start_time, end_time, granularity, opts, dg) {
 365   var formatter = /** @type{AxisLabelFormatter} */(
 366       opts("axisLabelFormatter"));
 367   var ticks = [];
 368   var t;
 369
 370   if (granularity < Dygraph.MONTHLY) {
 371     // Generate one tick mark for every fixed interval of time.
 372     var spacing = Dygraph.SHORT_SPACINGS[granularity];
 373
 374     // Find a time less than start_time which occurs on a "nice" time boundary
 375     // for this granularity.
 376     var g = spacing / 1000;
 377     var d = new Date(start_time);
 378     Dygraph.setDateSameTZ(d, {ms: 0});
 379
 380     var x;
 381     if (g <= 60) {  // seconds
 382       x = d.getSeconds();
 383       Dygraph.setDateSameTZ(d, {s: x - x % g});
 384     } else {
 385       Dygraph.setDateSameTZ(d, {s: 0});
 386       g /= 60;
 387       if (g <= 60) {  // minutes
 388         x = d.getMinutes();
 389         Dygraph.setDateSameTZ(d, {m: x - x % g});
 390       } else {
 391         Dygraph.setDateSameTZ(d, {m: 0});
 392         g /= 60;
 393
 394         if (g <= 24) {  // days
 395           x = d.getHours();
 396           d.setHours(x - x % g);
 397         } else {
 398           d.setHours(0);
 399           g /= 24;
 400
 401           if (g == 7) {  // one week
 402             d.setDate(d.getDate() - d.getDay());
 403           }
 404         }
 405       }
 406     }
 407     start_time = d.getTime();
 408
 409     // For spacings coarser than two-hourly, we want to ignore daylight
 410     // savings transitions to get consistent ticks. For finer-grained ticks,
 411     // it's essential to show the DST transition in all its messiness.
 412     var start_offset_min = new Date(start_time).getTimezoneOffset();
 413     var check_dst = (spacing >= Dygraph.SHORT_SPACINGS[Dygraph.TWO_HOURLY]);
 414
 415     for (t = start_time; t <= end_time; t += spacing) {
 416       d = new Date(t);
 417
 418       // This ensures that we stay on the same hourly "rhythm" across
 419       // daylight savings transitions. Without this, the ticks could get off
 420       // by an hour. See tests/daylight-savings.html or issue 147.
 421       if (check_dst && d.getTimezoneOffset() != start_offset_min) {
 422         var delta_min = d.getTimezoneOffset() - start_offset_min;
 423         t += delta_min * 60 * 1000;
 424         d = new Date(t);
 425         start_offset_min = d.getTimezoneOffset();
 426
 427         // Check whether we've backed into the previous timezone again.
 428         // This can happen during a "spring forward" transition. In this case,
 429         // it's best to skip this tick altogether (we may be shooting for a
 430         // non-existent time like the 2AM that's skipped) and go to the next
 431         // one.
 432         if (new Date(t + spacing).getTimezoneOffset() != start_offset_min) {
 433           t += spacing;
 434           d = new Date(t);
 435           start_offset_min = d.getTimezoneOffset();
 436         }
 437       }
 438
 439       ticks.push({ v:t,
 440                    label: formatter(d, granularity, opts, dg)
 441                  });
 442     }
 443   } else {
 444     // Display a tick mark on the first of a set of months of each year.
 445     // Years get a tick mark iff y % year_mod == 0. This is useful for
 446     // displaying a tick mark once every 10 years, say, on long time scales.
 447     var months;
 448     var year_mod = 1;  // e.g. to only print one point every 10 years.
 449
 450     if (granularity < Dygraph.NUM_GRANULARITIES) {
 451       months = Dygraph.LONG_TICK_PLACEMENTS[granularity].months;
 452       year_mod = Dygraph.LONG_TICK_PLACEMENTS[granularity].year_mod;
 453     } else {
 454       Dygraph.warn("Span of dates is too long");
 455     }
 456
 457     var start_year = new Date(start_time).getFullYear();
 458     var end_year   = new Date(end_time).getFullYear();
 459     for (var i = start_year; i <= end_year; i++) {
 460       if (i % year_mod !== 0) continue;
 461       for (var j = 0; j < months.length; j++) {
 462         var dt = new Date(i, months[j], 1);
 463         dt.setFullYear(i);
 464         t = dt.getTime();
 465         if (t < start_time || t > end_time) continue;
 466         ticks.push({ v:t,
 467                      label: formatter(new Date(t), granularity, opts, dg)
 468                    });
 469       }
 470     }
 471   }
 472
 473   return ticks;
 474 };
 475
 476 // These are set here so that this file can be included after dygraph.js
 477 // or independently.
 478 if (Dygraph &&
 479     Dygraph.DEFAULT_ATTRS &&
 480     Dygraph.DEFAULT_ATTRS['axes'] &&
 481     Dygraph.DEFAULT_ATTRS['axes']['x'] &&
 482     Dygraph.DEFAULT_ATTRS['axes']['y'] &&
 483     Dygraph.DEFAULT_ATTRS['axes']['y2']) {
 484   Dygraph.DEFAULT_ATTRS['axes']['x']['ticker'] = Dygraph.dateTicker;
 485   Dygraph.DEFAULT_ATTRS['axes']['y']['ticker'] = Dygraph.numericTicks;
 486   Dygraph.DEFAULT_ATTRS['axes']['y2']['ticker'] = Dygraph.numericTicks;
 487 }