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.numericTicks = function(a, b, pixels, opts, dygraph, vals) {
  66   var pixels_per_tick = opts('pixelsPerLabel');
  67   var ticks = [];
  68   var i, j, tickV, nTicks;
  69   if (vals) {
  70     for (i = 0; i < vals.length; i++) {
  71       ticks.push({v: vals[i]});
  72     }
  73   } else {
  74     // TODO(danvk): factor this log-scale block out into a separate function.
  75     if (opts("logscale")) {
  76       nTicks  = Math.floor(pixels / pixels_per_tick);
  77       var minIdx = Dygraph.binarySearch(a, Dygraph.PREFERRED_LOG_TICK_VALUES, 1);
  78       var maxIdx = Dygraph.binarySearch(b, Dygraph.PREFERRED_LOG_TICK_VALUES, -1);
  79       if (minIdx == -1) {
  80         minIdx = 0;
  81       }
  82       if (maxIdx == -1) {
  83         maxIdx = Dygraph.PREFERRED_LOG_TICK_VALUES.length - 1;
  84       }
  85       // Count the number of tick values would appear, if we can get at least
  86       // nTicks / 4 accept them.
  87       var lastDisplayed = null;
  88       if (maxIdx - minIdx >= nTicks / 4) {
  89         for (var idx = maxIdx; idx >= minIdx; idx--) {
  90           var tickValue = Dygraph.PREFERRED_LOG_TICK_VALUES[idx];
  91           var pixel_coord = Math.log(tickValue / a) / Math.log(b / a) * pixels;
  92           var tick = { v: tickValue };
  93           if (lastDisplayed === null) {
  94             lastDisplayed = {
  95               tickValue : tickValue,
  96               pixel_coord : pixel_coord
  97             };
  98           } else {
  99             if (Math.abs(pixel_coord - lastDisplayed.pixel_coord) >= pixels_per_tick) {
 100               lastDisplayed = {
 101                 tickValue : tickValue,
 102                 pixel_coord : pixel_coord
 103               };
 104             } else {
 105               tick.label = "";
 106             }
 107           }
 108           ticks.push(tick);
 109         }
 110         // Since we went in backwards order.
 111         ticks.reverse();
 112       }
 113     }
 114
 115     // ticks.length won't be 0 if the log scale function finds values to insert.
 116     if (ticks.length === 0) {
 117       // Basic idea:
 118       // Try labels every 1, 2, 5, 10, 20, 50, 100, etc.
 119       // Calculate the resulting tick spacing (i.e. this.height_ / nTicks).
 120       // The first spacing greater than pixelsPerYLabel is what we use.
 121       // TODO(danvk): version that works on a log scale.
 122       var kmg2 = opts("labelsKMG2");
 123       var mults;
 124       if (kmg2) {
 125         mults = [1, 2, 4, 8];
 126       } else {
 127         mults = [1, 2, 5];
 128       }
 129       var scale, low_val, high_val;
 130       for (i = -10; i < 50; i++) {
 131         var base_scale;
 132         if (kmg2) {
 133           base_scale = Math.pow(16, i);
 134         } else {
 135           base_scale = Math.pow(10, i);
 136         }
 137         var spacing = 0;
 138         for (j = 0; j < mults.length; j++) {
 139           scale = base_scale * mults[j];
 140           low_val = Math.floor(a / scale) * scale;
 141           high_val = Math.ceil(b / scale) * scale;
 142           nTicks = Math.abs(high_val - low_val) / scale;
 143           spacing = pixels / nTicks;
 144           // wish I could break out of both loops at once...
 145           if (spacing > pixels_per_tick) break;
 146         }
 147         if (spacing > pixels_per_tick) break;
 148       }
 149
 150       // Construct the set of ticks.
 151       // Allow reverse y-axis if it's explicitly requested.
 152       if (low_val > high_val) scale *= -1;
 153       for (i = 0; i < nTicks; i++) {
 154         tickV = low_val + i * scale;
 155         ticks.push( {v: tickV} );
 156       }
 157     }
 158   }
 159
 160   // Add formatted labels to the ticks.
 161   var k;
 162   var k_labels = [];
 163   if (opts("labelsKMB")) {
 164     k = 1000;
 165     k_labels = [ "K", "M", "B", "T" ];
 166   }
 167   if (opts("labelsKMG2")) {
 168     if (k) Dygraph.warn("Setting both labelsKMB and labelsKMG2. Pick one!");
 169     k = 1024;
 170     k_labels = [ "k", "M", "G", "T" ];
 171   }
 172
 173   var formatter = opts('axisLabelFormatter');
 174
 175   // Add labels to the ticks.
 176   for (i = 0; i < ticks.length; i++) {
 177     if (ticks[i].label !== undefined) continue;  // Use current label.
 178     tickV = ticks[i].v;
 179     var absTickV = Math.abs(tickV);
 180     // TODO(danvk): set granularity to something appropriate here.
 181     var label = formatter(tickV, 0, opts, dygraph);
 182     if (k_labels.length > 0) {
 183       // TODO(danvk): should this be integrated into the axisLabelFormatter?
 184       // Round up to an appropriate unit.
 185       var n = k*k*k*k;
 186       for (j = 3; j >= 0; j--, n /= k) {
 187         if (absTickV >= n) {
 188           label = Dygraph.round_(tickV / n, opts('digitsAfterDecimal')) +
 189               k_labels[j];
 190           break;
 191         }
 192       }
 193     }
 194     ticks[i].label = label;
 195   }
 196
 197   return ticks;
 198 };
 199
 200
 201 Dygraph.dateTicker = function(a, b, pixels, opts, dygraph, vals) {
 202   var chosen = Dygraph.pickDateTickGranularity(a, b, pixels, opts);
 203
 204   if (chosen >= 0) {
 205     return Dygraph.getDateAxis(a, b, chosen, opts, dygraph);
 206   } else {
 207     // this can happen if self.width_ is zero.
 208     return [];
 209   }
 210 };
 211
 212 // Time granularity enumeration
 213 Dygraph.SECONDLY = 0;
 214 Dygraph.TWO_SECONDLY = 1;
 215 Dygraph.FIVE_SECONDLY = 2;
 216 Dygraph.TEN_SECONDLY = 3;
 217 Dygraph.THIRTY_SECONDLY  = 4;
 218 Dygraph.MINUTELY = 5;
 219 Dygraph.TWO_MINUTELY = 6;
 220 Dygraph.FIVE_MINUTELY = 7;
 221 Dygraph.TEN_MINUTELY = 8;
 222 Dygraph.THIRTY_MINUTELY = 9;
 223 Dygraph.HOURLY = 10;
 224 Dygraph.TWO_HOURLY = 11;
 225 Dygraph.SIX_HOURLY = 12;
 226 Dygraph.DAILY = 13;
 227 Dygraph.WEEKLY = 14;
 228 Dygraph.MONTHLY = 15;
 229 Dygraph.QUARTERLY = 16;
 230 Dygraph.BIANNUAL = 17;
 231 Dygraph.ANNUAL = 18;
 232 Dygraph.DECADAL = 19;
 233 Dygraph.CENTENNIAL = 20;
 234 Dygraph.NUM_GRANULARITIES = 21;
 235
 236 Dygraph.SHORT_SPACINGS = [];
 237 Dygraph.SHORT_SPACINGS[Dygraph.SECONDLY]        = 1000 * 1;
 238 Dygraph.SHORT_SPACINGS[Dygraph.TWO_SECONDLY]    = 1000 * 2;
 239 Dygraph.SHORT_SPACINGS[Dygraph.FIVE_SECONDLY]   = 1000 * 5;
 240 Dygraph.SHORT_SPACINGS[Dygraph.TEN_SECONDLY]    = 1000 * 10;
 241 Dygraph.SHORT_SPACINGS[Dygraph.THIRTY_SECONDLY] = 1000 * 30;
 242 Dygraph.SHORT_SPACINGS[Dygraph.MINUTELY]        = 1000 * 60;
 243 Dygraph.SHORT_SPACINGS[Dygraph.TWO_MINUTELY]    = 1000 * 60 * 2;
 244 Dygraph.SHORT_SPACINGS[Dygraph.FIVE_MINUTELY]   = 1000 * 60 * 5;
 245 Dygraph.SHORT_SPACINGS[Dygraph.TEN_MINUTELY]    = 1000 * 60 * 10;
 246 Dygraph.SHORT_SPACINGS[Dygraph.THIRTY_MINUTELY] = 1000 * 60 * 30;
 247 Dygraph.SHORT_SPACINGS[Dygraph.HOURLY]          = 1000 * 3600;
 248 Dygraph.SHORT_SPACINGS[Dygraph.TWO_HOURLY]      = 1000 * 3600 * 2;
 249 Dygraph.SHORT_SPACINGS[Dygraph.SIX_HOURLY]      = 1000 * 3600 * 6;
 250 Dygraph.SHORT_SPACINGS[Dygraph.DAILY]           = 1000 * 86400;
 251 Dygraph.SHORT_SPACINGS[Dygraph.WEEKLY]          = 1000 * 604800;
 252
 253 /**
 254  * @private
 255  * This is a list of human-friendly values at which to show tick marks on a log
 256  * scale. It is k * 10^n, where k=1..9 and n=-39..+39, so:
 257  * ..., 1, 2, 3, 4, 5, ..., 9, 10, 20, 30, ..., 90, 100, 200, 300, ...
 258  * NOTE: this assumes that Dygraph.LOG_SCALE = 10.
 259  */
 260 Dygraph.PREFERRED_LOG_TICK_VALUES = function() {
 261   var vals = [];
 262   for (var power = -39; power <= 39; power++) {
 263     var range = Math.pow(10, power);
 264     for (var mult = 1; mult <= 9; mult++) {
 265       var val = range * mult;
 266       vals.push(val);
 267     }
 268   }
 269   return vals;
 270 }();
 271
 272 /**
 273  * Determine the correct granularity of ticks on a date axis.
 274  *
 275  * @param {Number} a Left edge of the chart (ms)
 276  * @param {Number} b Right edge of the chart (ms)
 277  * @param {Number} pixels Size of the chart in the relevant dimension (width).
 278  * @param {Function} opts Function mapping from option name -> value.
 279  * @return {Number} The appropriate axis granularity for this chart. See the
 280  * enumeration of possible values in dygraph-tickers.js.
 281  */
 282 Dygraph.pickDateTickGranularity = function(a, b, pixels, opts) {
 283   var pixels_per_tick = opts('pixelsPerLabel');
 284   for (var i = 0; i < Dygraph.NUM_GRANULARITIES; i++) {
 285     var num_ticks = Dygraph.numDateTicks(a, b, i);
 286     if (pixels / num_ticks >= pixels_per_tick) {
 287       return i;
 288     }
 289   }
 290   return -1;
 291 };
 292
 293 Dygraph.numDateTicks = function(start_time, end_time, granularity) {
 294   if (granularity < Dygraph.MONTHLY) {
 295     // Generate one tick mark for every fixed interval of time.
 296     var spacing = Dygraph.SHORT_SPACINGS[granularity];
 297     return Math.floor(0.5 + 1.0 * (end_time - start_time) / spacing);
 298   } else {
 299     var year_mod = 1;  // e.g. to only print one point every 10 years.
 300     var num_months = 12;
 301     if (granularity == Dygraph.QUARTERLY) num_months = 3;
 302     if (granularity == Dygraph.BIANNUAL) num_months = 2;
 303     if (granularity == Dygraph.ANNUAL) num_months = 1;
 304     if (granularity == Dygraph.DECADAL) { num_months = 1; year_mod = 10; }
 305     if (granularity == Dygraph.CENTENNIAL) { num_months = 1; year_mod = 100; }
 306
 307     var msInYear = 365.2524 * 24 * 3600 * 1000;
 308     var num_years = 1.0 * (end_time - start_time) / msInYear;
 309     return Math.floor(0.5 + 1.0 * num_years * num_months / year_mod);
 310   }
 311 };
 312
 313 Dygraph.getDateAxis = function(start_time, end_time, granularity, opts, dg) {
 314   var formatter = opts("axisLabelFormatter");
 315   var ticks = [];
 316   var t;
 317
 318   if (granularity < Dygraph.MONTHLY) {
 319     // Generate one tick mark for every fixed interval of time.
 320     var spacing = Dygraph.SHORT_SPACINGS[granularity];
 321
 322     // Find a time less than start_time which occurs on a "nice" time boundary
 323     // for this granularity.
 324     var g = spacing / 1000;
 325     var d = new Date(start_time);
 326     var x;
 327     if (g <= 60) {  // seconds
 328       x = d.getSeconds(); d.setSeconds(x - x % g);
 329     } else {
 330       d.setSeconds(0);
 331       g /= 60;
 332       if (g <= 60) {  // minutes
 333         x = d.getMinutes(); d.setMinutes(x - x % g);
 334       } else {
 335         d.setMinutes(0);
 336         g /= 60;
 337
 338         if (g <= 24) {  // days
 339           x = d.getHours(); d.setHours(x - x % g);
 340         } else {
 341           d.setHours(0);
 342           g /= 24;
 343
 344           if (g == 7) {  // one week
 345             d.setDate(d.getDate() - d.getDay());
 346           }
 347         }
 348       }
 349     }
 350     start_time = d.getTime();
 351
 352     for (t = start_time; t <= end_time; t += spacing) {
 353       ticks.push({ v:t,
 354                    label: formatter(new Date(t), granularity, opts, dg)
 355                  });
 356     }
 357   } else {
 358     // Display a tick mark on the first of a set of months of each year.
 359     // Years get a tick mark iff y % year_mod == 0. This is useful for
 360     // displaying a tick mark once every 10 years, say, on long time scales.
 361     var months;
 362     var year_mod = 1;  // e.g. to only print one point every 10 years.
 363
 364     if (granularity == Dygraph.MONTHLY) {
 365       months = [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 ];
 366     } else if (granularity == Dygraph.QUARTERLY) {
 367       months = [ 0, 3, 6, 9 ];
 368     } else if (granularity == Dygraph.BIANNUAL) {
 369       months = [ 0, 6 ];
 370     } else if (granularity == Dygraph.ANNUAL) {
 371       months = [ 0 ];
 372     } else if (granularity == Dygraph.DECADAL) {
 373       months = [ 0 ];
 374       year_mod = 10;
 375     } else if (granularity == Dygraph.CENTENNIAL) {
 376       months = [ 0 ];
 377       year_mod = 100;
 378     } else {
 379       Dygraph.warn("Span of dates is too long");
 380     }
 381
 382     var start_year = new Date(start_time).getFullYear();
 383     var end_year   = new Date(end_time).getFullYear();
 384     var zeropad = Dygraph.zeropad;
 385     for (var i = start_year; i <= end_year; i++) {
 386       if (i % year_mod !== 0) continue;
 387       for (var j = 0; j < months.length; j++) {
 388         var date_str = i + "/" + zeropad(1 + months[j]) + "/01";
 389         t = Dygraph.dateStrToMillis(date_str);
 390         if (t < start_time || t > end_time) continue;
 391         ticks.push({ v:t,
 392                      label: formatter(new Date(t), granularity, opts, dg)
 393                    });
 394       }
 395     }
 396   }
 397
 398   return ticks;
 399 };
 400
 401 // These are set here so that this file can be included after dygraph.js.
 402 Dygraph.DEFAULT_ATTRS.axes.x.ticker = Dygraph.dateTicker;
 403 Dygraph.DEFAULT_ATTRS.axes.y.ticker = Dygraph.numericTicks;
 404 Dygraph.DEFAULT_ATTRS.axes.y2.ticker = Dygraph.numericTicks;