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 */
  62 /*global Dygraph:false */
  63 "use strict";
  64
  65 Dygraph.numericLinearTicks = function(a, b, pixels, opts, dygraph, vals) {
  66   var nonLogscaleOpts = function(opt) {
  67     if (opt === 'logscale') return false;
  68     return opts(opt);
  69   };
  70   return Dygraph.numericTicks(a, b, pixels, nonLogscaleOpts, dygraph, vals);
  71 };
  72
  73 Dygraph.numericTicks = function(a, b, pixels, opts, dygraph, vals) {
  74   var pixels_per_tick = opts('pixelsPerLabel');
  75   var ticks = [];
  76   var i, j, tickV, nTicks;
  77   if (vals) {
  78     for (i = 0; i < vals.length; i++) {
  79       ticks.push({v: vals[i]});
  80     }
  81   } else {
  82     // TODO(danvk): factor this log-scale block out into a separate function.
  83     if (opts("logscale")) {
  84       nTicks  = Math.floor(pixels / pixels_per_tick);
  85       var minIdx = Dygraph.binarySearch(a, Dygraph.PREFERRED_LOG_TICK_VALUES, 1);
  86       var maxIdx = Dygraph.binarySearch(b, Dygraph.PREFERRED_LOG_TICK_VALUES, -1);
  87       if (minIdx == -1) {
  88         minIdx = 0;
  89       }
  90       if (maxIdx == -1) {
  91         maxIdx = Dygraph.PREFERRED_LOG_TICK_VALUES.length - 1;
  92       }
  93       // Count the number of tick values would appear, if we can get at least
  94       // nTicks / 4 accept them.
  95       var lastDisplayed = null;
  96       if (maxIdx - minIdx >= nTicks / 4) {
  97         for (var idx = maxIdx; idx >= minIdx; idx--) {
  98           var tickValue = Dygraph.PREFERRED_LOG_TICK_VALUES[idx];
  99           var pixel_coord = Math.log(tickValue / a) / Math.log(b / a) * pixels;
 100           var tick = { v: tickValue };
 101           if (lastDisplayed === null) {
 102             lastDisplayed = {
 103               tickValue : tickValue,
 104               pixel_coord : pixel_coord
 105             };
 106           } else {
 107             if (Math.abs(pixel_coord - lastDisplayed.pixel_coord) >= pixels_per_tick) {
 108               lastDisplayed = {
 109                 tickValue : tickValue,
 110                 pixel_coord : pixel_coord
 111               };
 112             } else {
 113               tick.label = "";
 114             }
 115           }
 116           ticks.push(tick);
 117         }
 118         // Since we went in backwards order.
 119         ticks.reverse();
 120       }
 121     }
 122
 123     // ticks.length won't be 0 if the log scale function finds values to insert.
 124     if (ticks.length === 0) {
 125       // Basic idea:
 126       // Try labels every 1, 2, 5, 10, 20, 50, 100, etc.
 127       // Calculate the resulting tick spacing (i.e. this.height_ / nTicks).
 128       // The first spacing greater than pixelsPerYLabel is what we use.
 129       // TODO(danvk): version that works on a log scale.
 130       var kmg2 = opts("labelsKMG2");
 131       var mults;
 132       if (kmg2) {
 133         mults = [1, 2, 4, 8];
 134       } else {
 135         mults = [1, 2, 5];
 136       }
 137       var scale, low_val, high_val;
 138       for (i = -10; i < 50; i++) {
 139         var base_scale;
 140         if (kmg2) {
 141           base_scale = Math.pow(16, i);
 142         } else {
 143           base_scale = Math.pow(10, i);
 144         }
 145         var spacing = 0;
 146         for (j = 0; j < mults.length; j++) {
 147           scale = base_scale * mults[j];
 148           low_val = Math.floor(a / scale) * scale;
 149           high_val = Math.ceil(b / scale) * scale;
 150           nTicks = Math.abs(high_val - low_val) / scale;
 151           spacing = pixels / nTicks;
 152           // wish I could break out of both loops at once...
 153           if (spacing > pixels_per_tick) break;
 154         }
 155         if (spacing > pixels_per_tick) break;
 156       }
 157
 158       // Construct the set of ticks.
 159       // Allow reverse y-axis if it's explicitly requested.
 160       if (low_val > high_val) scale *= -1;
 161       for (i = 0; i < nTicks; i++) {
 162         tickV = low_val + i * scale;
 163         ticks.push( {v: tickV} );
 164       }
 165     }
 166   }
 167
 168   // Add formatted labels to the ticks.
 169   var k;
 170   var k_labels = [];
 171   if (opts("labelsKMB")) {
 172     k = 1000;
 173     k_labels = [ "K", "M", "B", "T", "Q" ];
 174   }
 175   if (opts("labelsKMG2")) {
 176     if (k) Dygraph.warn("Setting both labelsKMB and labelsKMG2. Pick one!");
 177     k = 1024;
 178     k_labels = [ "k", "M", "G", "T", "P", "E" ];
 179   }
 180
 181   var formatter = opts('axisLabelFormatter');
 182
 183   // Add labels to the ticks.
 184   for (i = 0; i < ticks.length; i++) {
 185     if (ticks[i].label !== undefined) continue;  // Use current label.
 186     tickV = ticks[i].v;
 187     var absTickV = Math.abs(tickV);
 188     // TODO(danvk): set granularity to something appropriate here.
 189     var label = formatter(tickV, 0, opts, dygraph);
 190     if (k_labels.length > 0) {
 191       // TODO(danvk): should this be integrated into the axisLabelFormatter?
 192       // Round up to an appropriate unit.
 193       var n = Math.pow(k, k_labels.length);
 194       for (j = k_labels.length - 1; j >= 0; j--, n /= k) {
 195         if (absTickV >= n) {
 196           label = Dygraph.round_(tickV / n, opts('digitsAfterDecimal')) +
 197               k_labels[j];
 198           break;
 199         }
 200       }
 201     }
 202     ticks[i].label = label;
 203   }
 204
 205   return ticks;
 206 };
 207
 208
 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 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 Dygraph.SHORT_SPACINGS = [];
 245 Dygraph.SHORT_SPACINGS[Dygraph.SECONDLY]        = 1000 * 1;
 246 Dygraph.SHORT_SPACINGS[Dygraph.TWO_SECONDLY]    = 1000 * 2;
 247 Dygraph.SHORT_SPACINGS[Dygraph.FIVE_SECONDLY]   = 1000 * 5;
 248 Dygraph.SHORT_SPACINGS[Dygraph.TEN_SECONDLY]    = 1000 * 10;
 249 Dygraph.SHORT_SPACINGS[Dygraph.THIRTY_SECONDLY] = 1000 * 30;
 250 Dygraph.SHORT_SPACINGS[Dygraph.MINUTELY]        = 1000 * 60;
 251 Dygraph.SHORT_SPACINGS[Dygraph.TWO_MINUTELY]    = 1000 * 60 * 2;
 252 Dygraph.SHORT_SPACINGS[Dygraph.FIVE_MINUTELY]   = 1000 * 60 * 5;
 253 Dygraph.SHORT_SPACINGS[Dygraph.TEN_MINUTELY]    = 1000 * 60 * 10;
 254 Dygraph.SHORT_SPACINGS[Dygraph.THIRTY_MINUTELY] = 1000 * 60 * 30;
 255 Dygraph.SHORT_SPACINGS[Dygraph.HOURLY]          = 1000 * 3600;
 256 Dygraph.SHORT_SPACINGS[Dygraph.TWO_HOURLY]      = 1000 * 3600 * 2;
 257 Dygraph.SHORT_SPACINGS[Dygraph.SIX_HOURLY]      = 1000 * 3600 * 6;
 258 Dygraph.SHORT_SPACINGS[Dygraph.DAILY]           = 1000 * 86400;
 259 Dygraph.SHORT_SPACINGS[Dygraph.WEEKLY]          = 1000 * 604800;
 260
 261 /**
 262  * @private
 263  * This is a list of human-friendly values at which to show tick marks on a log
 264  * scale. It is k * 10^n, where k=1..9 and n=-39..+39, so:
 265  * ..., 1, 2, 3, 4, 5, ..., 9, 10, 20, 30, ..., 90, 100, 200, 300, ...
 266  * NOTE: this assumes that Dygraph.LOG_SCALE = 10.
 267  */
 268 Dygraph.PREFERRED_LOG_TICK_VALUES = function() {
 269   var vals = [];
 270   for (var power = -39; power <= 39; power++) {
 271     var range = Math.pow(10, power);
 272     for (var mult = 1; mult <= 9; mult++) {
 273       var val = range * mult;
 274       vals.push(val);
 275     }
 276   }
 277   return vals;
 278 }();
 279
 280 /**
 281  * Determine the correct granularity of ticks on a date axis.
 282  *
 283  * @param {Number} a Left edge of the chart (ms)
 284  * @param {Number} b Right edge of the chart (ms)
 285  * @param {Number} pixels Size of the chart in the relevant dimension (width).
 286  * @param {Function} opts Function mapping from option name -> value.
 287  * @return {Number} The appropriate axis granularity for this chart. See the
 288  * enumeration of possible values in dygraph-tickers.js.
 289  */
 290 Dygraph.pickDateTickGranularity = function(a, b, pixels, opts) {
 291   var pixels_per_tick = opts('pixelsPerLabel');
 292   for (var i = 0; i < Dygraph.NUM_GRANULARITIES; i++) {
 293     var num_ticks = Dygraph.numDateTicks(a, b, i);
 294     if (pixels / num_ticks >= pixels_per_tick) {
 295       return i;
 296     }
 297   }
 298   return -1;
 299 };
 300
 301 Dygraph.numDateTicks = function(start_time, end_time, granularity) {
 302   if (granularity < Dygraph.MONTHLY) {
 303     // Generate one tick mark for every fixed interval of time.
 304     var spacing = Dygraph.SHORT_SPACINGS[granularity];
 305     return Math.floor(0.5 + 1.0 * (end_time - start_time) / spacing);
 306   } else {
 307     var year_mod = 1;  // e.g. to only print one point every 10 years.
 308     var num_months = 12;
 309     if (granularity == Dygraph.QUARTERLY) num_months = 3;
 310     if (granularity == Dygraph.BIANNUAL) num_months = 2;
 311     if (granularity == Dygraph.ANNUAL) num_months = 1;
 312     if (granularity == Dygraph.DECADAL) { num_months = 1; year_mod = 10; }
 313     if (granularity == Dygraph.CENTENNIAL) { num_months = 1; year_mod = 100; }
 314
 315     var msInYear = 365.2524 * 24 * 3600 * 1000;
 316     var num_years = 1.0 * (end_time - start_time) / msInYear;
 317     return Math.floor(0.5 + 1.0 * num_years * num_months / year_mod);
 318   }
 319 };
 320
 321 Dygraph.getDateAxis = function(start_time, end_time, granularity, opts, dg) {
 322   var formatter = opts("axisLabelFormatter");
 323   var ticks = [];
 324   var t;
 325
 326   if (granularity < Dygraph.MONTHLY) {
 327     // Generate one tick mark for every fixed interval of time.
 328     var spacing = Dygraph.SHORT_SPACINGS[granularity];
 329
 330     // Find a time less than start_time which occurs on a "nice" time boundary
 331     // for this granularity.
 332     var g = spacing / 1000;
 333     var d = new Date(start_time);
 334     d.setMilliseconds(0);
 335     var x;
 336     if (g <= 60) {  // seconds
 337       x = d.getSeconds(); d.setSeconds(x - x % g);
 338     } else {
 339       d.setSeconds(0);
 340       g /= 60;
 341       if (g <= 60) {  // minutes
 342         x = d.getMinutes(); d.setMinutes(x - x % g);
 343       } else {
 344         d.setMinutes(0);
 345         g /= 60;
 346
 347         if (g <= 24) {  // days
 348           x = d.getHours(); d.setHours(x - x % g);
 349         } else {
 350           d.setHours(0);
 351           g /= 24;
 352
 353           if (g == 7) {  // one week
 354             d.setDate(d.getDate() - d.getDay());
 355           }
 356         }
 357       }
 358     }
 359     start_time = d.getTime();
 360
 361     for (t = start_time; t <= end_time; t += spacing) {
 362       ticks.push({ v:t,
 363                    label: formatter(new Date(t), granularity, opts, dg)
 364                  });
 365     }
 366   } else {
 367     // Display a tick mark on the first of a set of months of each year.
 368     // Years get a tick mark iff y % year_mod == 0. This is useful for
 369     // displaying a tick mark once every 10 years, say, on long time scales.
 370     var months;
 371     var year_mod = 1;  // e.g. to only print one point every 10 years.
 372
 373     if (granularity == Dygraph.MONTHLY) {
 374       months = [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 ];
 375     } else if (granularity == Dygraph.QUARTERLY) {
 376       months = [ 0, 3, 6, 9 ];
 377     } else if (granularity == Dygraph.BIANNUAL) {
 378       months = [ 0, 6 ];
 379     } else if (granularity == Dygraph.ANNUAL) {
 380       months = [ 0 ];
 381     } else if (granularity == Dygraph.DECADAL) {
 382       months = [ 0 ];
 383       year_mod = 10;
 384     } else if (granularity == Dygraph.CENTENNIAL) {
 385       months = [ 0 ];
 386       year_mod = 100;
 387     } else {
 388       Dygraph.warn("Span of dates is too long");
 389     }
 390
 391     var start_year = new Date(start_time).getFullYear();
 392     var end_year   = new Date(end_time).getFullYear();
 393     var zeropad = Dygraph.zeropad;
 394     for (var i = start_year; i <= end_year; i++) {
 395       if (i % year_mod !== 0) continue;
 396       for (var j = 0; j < months.length; j++) {
 397         var date_str = i + "/" + zeropad(1 + months[j]) + "/01";
 398         t = Dygraph.dateStrToMillis(date_str);
 399         if (t < start_time || t > end_time) continue;
 400         ticks.push({ v:t,
 401                      label: formatter(new Date(t), granularity, opts, dg)
 402                    });
 403       }
 404     }
 405   }
 406
 407   return ticks;
 408 };
 409
 410 // These are set here so that this file can be included after dygraph.js.
 411 Dygraph.DEFAULT_ATTRS.axes.x.ticker = Dygraph.dateTicker;
 412 Dygraph.DEFAULT_ATTRS.axes.y.ticker = Dygraph.numericTicks;
 413 Dygraph.DEFAULT_ATTRS.axes.y2.ticker = Dygraph.numericTicks;