| license: gpl-3.0 | |
| redirect: https://observablehq.com/@d3/d3-horizon-chart |
Horizon charts combine position and color to reduce vertical space. Start with a standard area chart, then mirror negative values (in blue) or offset them vertically. Click the + button above to increase the number of bands, turning the area into a horizon.
Implemented with the d3.horizon plugin.
| (function() { | |
| d3.horizon = function() { | |
| var bands = 1, // between 1 and 5, typically | |
| mode = "offset", // or mirror | |
| interpolate = "linear", // or basis, monotone, step-before, etc. | |
| x = d3_horizonX, | |
| y = d3_horizonY, | |
| w = 960, | |
| h = 40, | |
| duration = 0; | |
| var color = d3.scale.linear() | |
| .domain([-1, 0, 0, 1]) | |
| .range(["#08519c", "#bdd7e7", "#bae4b3", "#006d2c"]); | |
| // For each small multiple… | |
| function horizon(g) { | |
| g.each(function(d, i) { | |
| var g = d3.select(this), | |
| n = 2 * bands + 1, | |
| xMin = Infinity, | |
| xMax = -Infinity, | |
| yMax = -Infinity, | |
| x0, // old x-scale | |
| y0, // old y-scale | |
| id; // unique id for paths | |
| // Compute x- and y-values along with extents. | |
| var data = d.map(function(d, i) { | |
| var xv = x.call(this, d, i), | |
| yv = y.call(this, d, i); | |
| if (xv < xMin) xMin = xv; | |
| if (xv > xMax) xMax = xv; | |
| if (-yv > yMax) yMax = -yv; | |
| if (yv > yMax) yMax = yv; | |
| return [xv, yv]; | |
| }); | |
| // Compute the new x- and y-scales, and transform. | |
| var x1 = d3.scale.linear().domain([xMin, xMax]).range([0, w]), | |
| y1 = d3.scale.linear().domain([0, yMax]).range([0, h * bands]), | |
| t1 = d3_horizonTransform(bands, h, mode); | |
| // Retrieve the old scales, if this is an update. | |
| if (this.__chart__) { | |
| x0 = this.__chart__.x; | |
| y0 = this.__chart__.y; | |
| t0 = this.__chart__.t; | |
| id = this.__chart__.id; | |
| } else { | |
| x0 = x1.copy(); | |
| y0 = y1.copy(); | |
| t0 = t1; | |
| id = ++d3_horizonId; | |
| } | |
| // We'll use a defs to store the area path and the clip path. | |
| var defs = g.selectAll("defs") | |
| .data([null]); | |
| // The clip path is a simple rect. | |
| defs.enter().append("defs").append("clipPath") | |
| .attr("id", "d3_horizon_clip" + id) | |
| .append("rect") | |
| .attr("width", w) | |
| .attr("height", h); | |
| defs.select("rect").transition() | |
| .duration(duration) | |
| .attr("width", w) | |
| .attr("height", h); | |
| // We'll use a container to clip all horizon layers at once. | |
| g.selectAll("g") | |
| .data([null]) | |
| .enter().append("g") | |
| .attr("clip-path", "url(#d3_horizon_clip" + id + ")"); | |
| // Instantiate each copy of the path with different transforms. | |
| var path = g.select("g").selectAll("path") | |
| .data(d3.range(-1, -bands - 1, -1).concat(d3.range(1, bands + 1)), Number); | |
| var d0 = d3_horizonArea | |
| .interpolate(interpolate) | |
| .x(function(d) { return x0(d[0]); }) | |
| .y0(h * bands) | |
| .y1(function(d) { return h * bands - y0(d[1]); }) | |
| (data); | |
| var d1 = d3_horizonArea | |
| .x(function(d) { return x1(d[0]); }) | |
| .y1(function(d) { return h * bands - y1(d[1]); }) | |
| (data); | |
| path.enter().append("path") | |
| .style("fill", color) | |
| .attr("transform", t0) | |
| .attr("d", d0); | |
| path.transition() | |
| .duration(duration) | |
| .style("fill", color) | |
| .attr("transform", t1) | |
| .attr("d", d1); | |
| path.exit().transition() | |
| .duration(duration) | |
| .attr("transform", t1) | |
| .attr("d", d1) | |
| .remove(); | |
| // Stash the new scales. | |
| this.__chart__ = {x: x1, y: y1, t: t1, id: id}; | |
| }); | |
| d3.timer.flush(); | |
| } | |
| horizon.duration = function(x) { | |
| if (!arguments.length) return duration; | |
| duration = +x; | |
| return horizon; | |
| }; | |
| horizon.bands = function(x) { | |
| if (!arguments.length) return bands; | |
| bands = +x; | |
| color.domain([-bands, 0, 0, bands]); | |
| return horizon; | |
| }; | |
| horizon.mode = function(x) { | |
| if (!arguments.length) return mode; | |
| mode = x + ""; | |
| return horizon; | |
| }; | |
| horizon.colors = function(x) { | |
| if (!arguments.length) return color.range(); | |
| color.range(x); | |
| return horizon; | |
| }; | |
| horizon.interpolate = function(x) { | |
| if (!arguments.length) return interpolate; | |
| interpolate = x + ""; | |
| return horizon; | |
| }; | |
| horizon.x = function(z) { | |
| if (!arguments.length) return x; | |
| x = z; | |
| return horizon; | |
| }; | |
| horizon.y = function(z) { | |
| if (!arguments.length) return y; | |
| y = z; | |
| return horizon; | |
| }; | |
| horizon.width = function(x) { | |
| if (!arguments.length) return w; | |
| w = +x; | |
| return horizon; | |
| }; | |
| horizon.height = function(x) { | |
| if (!arguments.length) return h; | |
| h = +x; | |
| return horizon; | |
| }; | |
| return horizon; | |
| }; | |
| var d3_horizonArea = d3.svg.area(), | |
| d3_horizonId = 0; | |
| function d3_horizonX(d) { | |
| return d[0]; | |
| } | |
| function d3_horizonY(d) { | |
| return d[1]; | |
| } | |
| function d3_horizonTransform(bands, h, mode) { | |
| return mode == "offset" | |
| ? function(d) { return "translate(0," + (d + (d < 0) - bands) * h + ")"; } | |
| : function(d) { return (d < 0 ? "scale(1,-1)" : "") + "translate(0," + (d - bands) * h + ")"; }; | |
| } | |
| })(); |
| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| body { | |
| font-family: sans-serif; | |
| } | |
| svg { | |
| position: absolute; | |
| top: 0; | |
| } | |
| #horizon-controls { | |
| position: absolute; | |
| width: 940px; | |
| padding: 10px; | |
| z-index: 1; | |
| } | |
| #horizon-bands { | |
| float: right; | |
| } | |
| </style> | |
| <div id="horizon-controls"> | |
| <input name="mode" type="radio" value="mirror" id="horizon-mode-mirror" checked><label for="horizon-mode-mirror"> Mirror</label> | |
| <input name="mode" type="radio" value="offset" id="horizon-mode-offset"><label for="horizon-mode-offset"> Offset</label> | |
| <span id="horizon-bands"><span id="horizon-bands-value">1</span> <button class="first">−</button><button class="last">+</button></span> | |
| </div> | |
| <div id="horizon-chart"></div> | |
| <script src="//d3js.org/d3.v3.min.js"></script> | |
| <script src="horizon.js?0.0.1"></script> | |
| <script> | |
| var width = 960, | |
| height = 500; | |
| var chart = d3.horizon() | |
| .width(width) | |
| .height(height) | |
| .bands(1) | |
| .mode("mirror") | |
| .interpolate("basis"); | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height); | |
| d3.json("unemployment.json", function(error, data) { | |
| if (error) throw error; | |
| // Offset so that positive is above-average and negative is below-average. | |
| var mean = data.rate.reduce(function(p, v) { return p + v; }, 0) / data.rate.length; | |
| // Transpose column values to rows. | |
| data = data.rate.map(function(rate, i) { | |
| return [Date.UTC(data.year[i], data.month[i] - 1), rate - mean]; | |
| }); | |
| // Render the chart. | |
| svg.data([data]).call(chart); | |
| // Enable mode buttons. | |
| d3.selectAll("#horizon-controls input[name=mode]").on("change", function() { | |
| svg.call(chart.duration(0).mode(this.value)); | |
| }); | |
| // Enable bands buttons. | |
| d3.selectAll("#horizon-bands button").data([-1, 1]).on("click", function(d) { | |
| var n = Math.max(1, chart.bands() + d); | |
| d3.select("#horizon-bands-value").text(n); | |
| svg.call(chart.duration(1000).bands(n).height(height / n)); | |
| }); | |
| }); | |
| </script> |
| {"year":[2000,2000,2000,2000,2000,2000,2000,2000,2000,2000,2000,2000,2001,2001,2001,2001,2001,2001,2001,2001,2001,2001,2001,2001,2002,2002,2002,2002,2002,2002,2002,2002,2002,2002,2002,2002,2003,2003,2003,2003,2003,2003,2003,2003,2003,2003,2003,2003,2004,2004,2004,2004,2004,2004,2004,2004,2004,2004,2004,2004,2005,2005,2005,2005,2005,2005,2005,2005,2005,2005,2005,2005,2006,2006,2006,2006,2006,2006,2006,2006,2006,2006,2006,2006,2007,2007,2007,2007,2007,2007,2007,2007,2007,2007,2007,2007,2008,2008,2008,2008,2008,2008,2008,2008,2008,2008,2008,2008,2009,2009,2009,2009,2009,2009,2009,2009,2009,2009,2009,2009,2010,2010],"month":[1,2,3,4,5,6,7,8,9,10,11,12,1,2,3,4,5,6,7,8,9,10,11,12,1,2,3,4,5,6,7,8,9,10,11,12,1,2,3,4,5,6,7,8,9,10,11,12,1,2,3,4,5,6,7,8,9,10,11,12,1,2,3,4,5,6,7,8,9,10,11,12,1,2,3,4,5,6,7,8,9,10,11,12,1,2,3,4,5,6,7,8,9,10,11,12,1,2,3,4,5,6,7,8,9,10,11,12,1,2,3,4,5,6,7,8,9,10,11,12,1,2],"rate":[4.5,4.4,4.3,3.7,3.8,4.1,4.2,4.1,3.8,3.6,3.7,3.7,4.7,4.6,4.5,4.2,4.1,4.7,4.7,4.9,4.7,5,5.3,5.4,6.3,6.1,6.1,5.7,5.5,6,5.9,5.7,5.4,5.3,5.6,5.7,6.5,6.4,6.2,5.8,5.8,6.5,6.3,6,5.8,5.6,5.6,5.4,6.3,6,6,5.4,5.3,5.8,5.7,5.4,5.1,5.1,5.2,5.1,5.7,5.8,5.4,4.9,4.9,5.2,5.2,4.9,4.8,4.6,4.8,4.6,5.1,5.1,4.8,4.5,4.4,4.8,5,4.6,4.4,4.1,4.3,4.3,5,4.9,4.5,4.3,4.3,4.7,4.9,4.6,4.5,4.4,4.5,4.8,5.4,5.2,5.2,4.8,5.2,5.7,6,6.1,6,6.1,6.5,7.1,8.5,8.9,9,8.6,9.1,9.7,9.7,9.6,9.5,9.5,9.4,9.7,10.6,10.4]} |
is there a way to set the y-axis domain for the horizon chart ? yMax is calculated on lines 34:35 and used in :41 but I see no interface to set it.