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 };