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