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 // Date components enumeration (in the order of the arguments in Date)
 245 // TODO: make this an @enum
 246 Dygraph.DATEFIELD_Y = 0;
 247 Dygraph.DATEFIELD_M = 1;
 248 Dygraph.DATEFIELD_D = 2;
 249 Dygraph.DATEFIELD_HH = 3;
 250 Dygraph.DATEFIELD_MM = 4;
 251 Dygraph.DATEFIELD_SS = 5;
 252 Dygraph.DATEFIELD_MS = 6;
 253 Dygraph.NUM_DATEFIELDS = 7;
 254
 255
 256 /** @type {Array.<{datefield:number, step:number, spacing:number}>} */
 257 Dygraph.TICK_PLACEMENT = [];
 258 Dygraph.TICK_PLACEMENT[Dygraph.SECONDLY]        = {datefield: Dygraph.DATEFIELD_SS, step:   1, spacing: 1000 * 1};
 259 Dygraph.TICK_PLACEMENT[Dygraph.TWO_SECONDLY]    = {datefield: Dygraph.DATEFIELD_SS, step:   2, spacing: 1000 * 2};
 260 Dygraph.TICK_PLACEMENT[Dygraph.FIVE_SECONDLY]   = {datefield: Dygraph.DATEFIELD_SS, step:   5, spacing: 1000 * 5};
 261 Dygraph.TICK_PLACEMENT[Dygraph.TEN_SECONDLY]    = {datefield: Dygraph.DATEFIELD_SS, step:  10, spacing: 1000 * 10};
 262 Dygraph.TICK_PLACEMENT[Dygraph.THIRTY_SECONDLY] = {datefield: Dygraph.DATEFIELD_SS, step:  30, spacing: 1000 * 30};
 263 Dygraph.TICK_PLACEMENT[Dygraph.MINUTELY]        = {datefield: Dygraph.DATEFIELD_MM, step:   1, spacing: 1000 * 60};
 264 Dygraph.TICK_PLACEMENT[Dygraph.TWO_MINUTELY]    = {datefield: Dygraph.DATEFIELD_MM, step:   2, spacing: 1000 * 60 * 2};
 265 Dygraph.TICK_PLACEMENT[Dygraph.FIVE_MINUTELY]   = {datefield: Dygraph.DATEFIELD_MM, step:   5, spacing: 1000 * 60 * 5};
 266 Dygraph.TICK_PLACEMENT[Dygraph.TEN_MINUTELY]    = {datefield: Dygraph.DATEFIELD_MM, step:  10, spacing: 1000 * 60 * 10};
 267 Dygraph.TICK_PLACEMENT[Dygraph.THIRTY_MINUTELY] = {datefield: Dygraph.DATEFIELD_MM, step:  30, spacing: 1000 * 60 * 30};
 268 Dygraph.TICK_PLACEMENT[Dygraph.HOURLY]          = {datefield: Dygraph.DATEFIELD_HH, step:   1, spacing: 1000 * 3600};
 269 Dygraph.TICK_PLACEMENT[Dygraph.TWO_HOURLY]      = {datefield: Dygraph.DATEFIELD_HH, step:   2, spacing: 1000 * 3600 * 2};
 270 Dygraph.TICK_PLACEMENT[Dygraph.SIX_HOURLY]      = {datefield: Dygraph.DATEFIELD_HH, step:   6, spacing: 1000 * 3600 * 6};
 271 Dygraph.TICK_PLACEMENT[Dygraph.DAILY]           = {datefield: Dygraph.DATEFIELD_D,  step:   1, spacing: 1000 * 86400};
 272 Dygraph.TICK_PLACEMENT[Dygraph.WEEKLY]          = {datefield: Dygraph.DATEFIELD_D,  step:   7, spacing: 1000 * 604800};
 273 Dygraph.TICK_PLACEMENT[Dygraph.MONTHLY]         = {datefield: Dygraph.DATEFIELD_M,  step:   1, spacing: 1000 * 7200  * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 / 12
 274 Dygraph.TICK_PLACEMENT[Dygraph.QUARTERLY]       = {datefield: Dygraph.DATEFIELD_M,  step:   3, spacing: 1000 * 21600 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 / 4
 275 Dygraph.TICK_PLACEMENT[Dygraph.BIANNUAL]        = {datefield: Dygraph.DATEFIELD_M,  step:   6, spacing: 1000 * 43200 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 / 2
 276 Dygraph.TICK_PLACEMENT[Dygraph.ANNUAL]          = {datefield: Dygraph.DATEFIELD_Y,  step:   1, spacing: 1000 * 86400   * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 * 1
 277 Dygraph.TICK_PLACEMENT[Dygraph.DECADAL]         = {datefield: Dygraph.DATEFIELD_Y,  step:  10, spacing: 1000 * 864000  * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 * 10
 278 Dygraph.TICK_PLACEMENT[Dygraph.CENTENNIAL]      = {datefield: Dygraph.DATEFIELD_Y,  step: 100, spacing: 1000 * 8640000 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 * 100
 279
 280
 281 /**
 282  * This is a list of human-friendly values at which to show tick marks on a log
 283  * scale. It is k * 10^n, where k=1..9 and n=-39..+39, so:
 284  * ..., 1, 2, 3, 4, 5, ..., 9, 10, 20, 30, ..., 90, 100, 200, 300, ...
 285  * NOTE: this assumes that Dygraph.LOG_SCALE = 10.
 286  * @type {Array.<number>}
 287  */
 288 Dygraph.PREFERRED_LOG_TICK_VALUES = function() {
 289   var vals = [];
 290   for (var power = -39; power <= 39; power++) {
 291     var range = Math.pow(10, power);
 292     for (var mult = 1; mult <= 9; mult++) {
 293       var val = range * mult;
 294       vals.push(val);
 295     }
 296   }
 297   return vals;
 298 }();
 299
 300 /**
 301  * Determine the correct granularity of ticks on a date axis.
 302  *
 303  * @param {number} a Left edge of the chart (ms)
 304  * @param {number} b Right edge of the chart (ms)
 305  * @param {number} pixels Size of the chart in the relevant dimension (width).
 306  * @param {function(string):*} opts Function mapping from option name -&gt; value.
 307  * @return {number} The appropriate axis granularity for this chart. See the
 308  *     enumeration of possible values in dygraph-tickers.js.
 309  */
 310 Dygraph.pickDateTickGranularity = function(a, b, pixels, opts) {
 311   var pixels_per_tick = /** @type{number} */(opts('pixelsPerLabel'));
 312   for (var i = 0; i < Dygraph.NUM_GRANULARITIES; i++) {
 313     var num_ticks = Dygraph.numDateTicks(a, b, i);
 314     if (pixels / num_ticks >= pixels_per_tick) {
 315       return i;
 316     }
 317   }
 318   return -1;
 319 };
 320
 321 /**
 322  * Compute the number of ticks on a date axis for a given granularity.
 323  * @param {number} start_time
 324  * @param {number} end_time
 325  * @param {number} granularity (one of the granularities enumerated above)
 326  * @return {number} (Approximate) number of ticks that would result.
 327  */
 328 Dygraph.numDateTicks = function(start_time, end_time, granularity) {
 329   var spacing = Dygraph.TICK_PLACEMENT[granularity].spacing;
 330   return Math.round(1.0 * (end_time - start_time) / spacing);
 331 };
 332
 333 /**
 334  * Compute the positions and labels of ticks on a date axis for a given granularity.
 335  * @param {number} start_time
 336  * @param {number} end_time
 337  * @param {number} granularity (one of the granularities enumerated above)
 338  * @param {function(string):*} opts Function mapping from option name -&gt; value.
 339  * @param {Dygraph=} dg
 340  * @return {!Dygraph.TickList}
 341  */
 342 Dygraph.getDateAxis = function(start_time, end_time, granularity, opts, dg) {
 343   var formatter = /** @type{AxisLabelFormatter} */(
 344       opts("axisLabelFormatter"));
 345   var utc = opts("labelsUTC");
 346   var accessors = utc ? Dygraph.DateAccessorsUTC : Dygraph.DateAccessorsLocal;
 347
 348   var datefield = Dygraph.TICK_PLACEMENT[granularity].datefield;
 349   var step = Dygraph.TICK_PLACEMENT[granularity].step;
 350   var spacing = Dygraph.TICK_PLACEMENT[granularity].spacing;
 351
 352   // Choose a nice tick position before the initial instant.
 353   // Currently, this code deals properly with the existent daily granularities:
 354   // DAILY (with step of 1) and WEEKLY (with step of 7 but specially handled).
 355   // Other daily granularities (say TWO_DAILY) should also be handled specially
 356   // by setting the start_date_offset to 0.
 357   var start_date = new Date(start_time);
 358   var date_array = [];
 359   date_array[Dygraph.DATEFIELD_Y]  = accessors.getFullYear(start_date);
 360   date_array[Dygraph.DATEFIELD_M]  = accessors.getMonth(start_date);
 361   date_array[Dygraph.DATEFIELD_D]  = accessors.getDate(start_date);
 362   date_array[Dygraph.DATEFIELD_HH] = accessors.getHours(start_date);
 363   date_array[Dygraph.DATEFIELD_MM] = accessors.getMinutes(start_date);
 364   date_array[Dygraph.DATEFIELD_SS] = accessors.getSeconds(start_date);
 365   date_array[Dygraph.DATEFIELD_MS] = accessors.getMilliseconds(start_date);
 366
 367   var start_date_offset = date_array[datefield] % step;
 368   if (granularity == Dygraph.WEEKLY) {
 369     // This will put the ticks on Sundays.
 370     start_date_offset = accessors.getDay(start_date);
 371   }
 372
 373   date_array[datefield] -= start_date_offset;
 374   for (var df = datefield + 1; df < Dygraph.NUM_DATEFIELDS; df++) {
 375     // The minimum value is 1 for the day of month, and 0 for all other fields.
 376     date_array[df] = (df === Dygraph.DATEFIELD_D) ? 1 : 0;
 377   }
 378
 379   // Generate the ticks.
 380   // For granularities not coarser than HOURLY we use the fact that:
 381   //   the number of milliseconds between ticks is constant
 382   //   and equal to the defined spacing.
 383   // Otherwise we rely on the 'roll over' property of the Date functions:
 384   //   when some date field is set to a value outside of its logical range,
 385   //   the excess 'rolls over' the next (more significant) field.
 386   // However, when using local time with DST transitions,
 387   // there are dates that do not represent any time value at all
 388   // (those in the hour skipped at the 'spring forward'),
 389   // and the JavaScript engines usually return an equivalent value.
 390   // Hence we have to check that the date is properly increased at each step,
 391   // returning a date at a nice tick position.
 392   var ticks = [];
 393   var tick_date = accessors.makeDate.apply(null, date_array);
 394   var tick_time = tick_date.getTime();
 395   if (granularity <= Dygraph.HOURLY) {
 396     if (tick_time < start_time) {
 397       tick_time += spacing;
 398       tick_date = new Date(tick_time);
 399     }
 400     while (tick_time <= end_time) {
 401       ticks.push({ v: tick_time,
 402                    label: formatter(tick_date, granularity, opts, dg)
 403                  });
 404       tick_time += spacing;
 405       tick_date = new Date(tick_time);
 406     }
 407   } else {
 408     if (tick_time < start_time) {
 409       date_array[datefield] += step;
 410       tick_date = accessors.makeDate.apply(null, date_array);
 411       tick_time = tick_date.getTime();
 412     }
 413     while (tick_time <= end_time) {
 414       if (granularity >= Dygraph.DAILY ||
 415           accessors.getHours(tick_date) % step === 0) {
 416         ticks.push({ v: tick_time,
 417                      label: formatter(tick_date, granularity, opts, dg)
 418                    });
 419       }
 420       date_array[datefield] += step;
 421       tick_date = accessors.makeDate.apply(null, date_array);
 422       tick_time = tick_date.getTime();
 423     }
 424   }
 425   return ticks;
 426 };
 427
 428 // These are set here so that this file can be included after dygraph.js
 429 // or independently.
 430 if (Dygraph &&
 431     Dygraph.DEFAULT_ATTRS &&
 432     Dygraph.DEFAULT_ATTRS['axes'] &&
 433     Dygraph.DEFAULT_ATTRS['axes']['x'] &&
 434     Dygraph.DEFAULT_ATTRS['axes']['y'] &&
 435     Dygraph.DEFAULT_ATTRS['axes']['y2']) {
 436   Dygraph.DEFAULT_ATTRS['axes']['x']['ticker'] = Dygraph.dateTicker;
 437   Dygraph.DEFAULT_ATTRS['axes']['y']['ticker'] = Dygraph.numericTicks;
 438   Dygraph.DEFAULT_ATTRS['axes']['y2']['ticker'] = Dygraph.numericTicks;
 439 }