From: Robert Konigsberg Date: Fri, 28 Jan 2011 19:59:51 +0000 (-0500) Subject: Much better algorithm for computing log scale ticks. X-Git-Tag: v1.0.0~587^2~12^2~7 X-Git-Url: https://adrianiainlam.tk/git/?a=commitdiff_plain;h=6821efbe1eb5ec469d4e8a320df9fa8716238c2d;p=dygraphs.git Much better algorithm for computing log scale ticks. --- diff --git a/dygraph.js b/dygraph.js index e19acad..9fa9a26 100644 --- a/dygraph.js +++ b/dygraph.js @@ -24,7 +24,6 @@ If the 'errorBars' option is set in the constructor, the input should be of the form - Date,SeriesA,SeriesB,... YYYYMMDD,A1,sigmaA1,B1,sigmaB1,... YYYYMMDD,A2,sigmaA2,B2,sigmaB2,... @@ -1914,6 +1913,19 @@ Dygraph.dateTicker = function(startDate, endDate, self) { } }; +Dygraph.DEFAULT_PREFERRED_LOG_TICK_VALUES = function() { + var vals = []; + for (var power = -39; power <= 39; power++) { + var range = Math.pow(10, power); + var mults = [1, 1.5, 2.5, 5, 7]; // [1,2,3,4,5,6,7,8,9]; + for (var multIdx = 0; multIdx < mults.length; multIdx++) { + var val = range * mults[multIdx]; + vals.push(val); + } + } + return vals; +}(); + /** * Add ticks when the x axis has numbers on it (instead of dates) * TODO(konigsberg): Update comment. @@ -1938,26 +1950,40 @@ Dygraph.numericTicks = function(minV, maxV, self, axis_props, vals) { } } else { if (axis_props && attr("logscale")) { - // As opposed to the other ways for computing ticks, we're just going - // for nearby values. There's no reasonable way to scale the values - // (unless we want to show strings like "log(" + x + ")") in which case - // x can be integer values. - - // so compute height / pixelsPerTick and move on. var pixelsPerTick = attr('pixelsPerYLabel'); // NOTE(konigsberg): Dan, should self.height_ be self.plotter_.area.h? var nTicks = Math.floor(self.height_ / pixelsPerTick); - var vv = minV; - var lmv = Dygraph.log10(minV); - var lxv = Dygraph.log10(maxV); - var logMultiplier = (lxv - lmv) / nTicks; - var multiplier = Math.pow(Dygraph.LOG_SCALE, logMultiplier); - // Construct the set of ticks. - for (var i = 0; i < nTicks; i++) { - ticks.push( {v: vv} ); - vv = vv * multiplier; + var minIdx = null; + var maxIdx = null; + // Count the number of tick values would appear, if we can get at least + // nTicks / 3 accept them. + for (var idx = 0; idx < Dygraph.DEFAULT_PREFERRED_LOG_TICK_VALUES.length; idx++) { + var v = Dygraph.DEFAULT_PREFERRED_LOG_TICK_VALUES[idx]; + if (v == minV && minIdx == null) { + minIdx = idx; + } + if (v > minV && minIdx == null && idx > 0) { + minIdx = idx - 1; + } + if (maxIdx == null && v >= maxV) { + maxIdx = idx; + break; // At this point we're done. + } } - } else { + if (minIdx == null) { + minIdx = 0; + } + if (maxIdx == null) { + maxIdx = Dygraph.DEFAULT_PREFERRED_LOG_TICK_VALUES.length - 1; + } + if ((maxIdx - minIdx) * 4 >= nTicks) { + for (var idx = minIdx; idx <= maxIdx; idx++) { + ticks.push({ v: Dygraph.DEFAULT_PREFERRED_LOG_TICK_VALUES[idx] }); + } + } + } + // ticks.length won't be 0 if the log scale function finds values to insert. + if (ticks.length == 0) { // Basic idea: // Try labels every 1, 2, 5, 10, 20, 50, 100, etc. // Calculate the resulting tick spacing (i.e. this.height_ / nTicks).