I don't remember how I found this library D3.js, probably while looking for something than Graphviz because I was not able to easily connect to draw a graph on a webpage. I discovered two days ago than a Python library (PIL) I used to recommend to my student was not maintained any more and had been replaced by another one (Pillow). To draw graph, I usually recommend Matplotlib but I was wondering why not trying another one and another language which allows animated graphs. So here are my first steps with D3.js which I intent to use to draw a very simple plot.
Before writing the script
The first step starts by create a spot on the webpage:
<div id="graphid"></div>It also requires data which I stored in a separate file marathon.txt:
city year time seconds PARIS 2011 02:06:29 7589 PARIS 2010 02:06:41 7601 PARIS 2009 02:05:47 7547 PARIS 2008 02:06:40 7600 PARIS 2007 02:07:17 7637 PARIS 2006 02:08:03 7683 ...I like the fact, every time I press F5, the browser opens up and show me my page. I use SciTE as a text editor. Simple but debugging is quite difficult. For that, I used Chrome to the error (look at option activate the debug console). Anyway, let's begin. It first requires to inclure the library:
<script src="http://d3js.org/d3.v3.js"></script>It can be placed in the header or in the body. You should then configure the style otherwise your graph may not have the look you are looking for:
<style> .axis path, .axis line { fill: none; stroke: #000; shape-rendering: crispEdges; } .x.axis path { display: none; } .line { fill: none; stroke: steelblue; stroke-width: 1.5px; } </style>
The script and the graph
// graph size var margin = {top: 20, right: 80, bottom: 30, left: 50} ; var width = 600 - margin.left - margin.right ; var height = 250 - margin.top - margin.bottom; var color = d3.scale.category10(); // we define the axis var x = d3.scale.linear().range([0, width]); var y = d3.scale.linear().range([height, 0]); var xAxis = d3.svg.axis().scale(x).orient("bottom"); var yAxis = d3.svg.axis().scale(y).orient("left"); // we choose the graph position (don't forget #) var svg = d3.select("#graphid").append("svg") .attr("width", width + margin.left + margin.right) .attr("height", height + margin.top + margin.bottom) .append("g") .attr("transform", "translate(" + margin.left + "," + margin.top + ")"); d3.tsv("documents/marathon.tsv", function(error, data) { // one color per city var colors = { "PARIS":"blue", "NEW YORK":"red", "STOCKOLM":"black", "LONDON":"yellow", "AMSTERDAM":"green", "FUKUOKA":"orange", "BERLIN":"purple", "BOSTON":"cyan", "CHICAGO":"magenta" } ; // we define the real columns // if data is undefined, use the debugger to watch error // which contains the reason why it does not properly load data.forEach(function(d) { d.year = +d.year; d.seconds = +d.seconds; d.color = colors[d.city] ; d.city = d.city ; }); // we define the axis limits x.domain(d3.extent(data, function(d) { return d.year; })).nice(); y.domain([d3.min(data, function(d) { return d.seconds; }), d3.max(data, function(d) { return d.seconds; })]); // we define the axis svg.append("g") .attr("class", "x axis") .attr("transform", "translate(0," + height + ")") .call(xAxis) .append("text") .attr("class", "label") .attr("x", width) .attr("y", -6) .style("text-anchor", "end") .text("year"); svg.append("g") .attr("class", "y axis") .call(yAxis) .append("text") .attr("class", "label") .attr("transform", "rotate(-90)") .attr("y", 6) .attr("dy", ".71em") .style("text-anchor", "end") .text("time(s)") // we define the data svg.selectAll(".dot") .data(data) .enter().append("circle") .attr("class", "dot") .attr("r", 3.5) .attr("cx", function(d) { return x(d.year); }) .attr("cy", function(d) { return y(d.seconds); }) .style("fill", function(d) { return color(d.color); }); // the legend var keys = [] for(var key in colors) { keys.push( key ); } var legend = svg.selectAll(".legend") .data(keys.slice()) .enter().append("g") .attr("class", "legend") .attr("transform", function(d, i) { return "translate(0," + i * 20 + ")"; }); legend.append("rect") .attr("x", width - 18) .attr("width", 18) .attr("height", 18) .style("fill", function(d) { return colors[d]; } ); legend.append("text") .attr("x", width - 24) .attr("y", 9) .attr("dy", ".35em") .style("text-anchor", "end") .text(function(d) { return d } ); });
Conclusion
Well, it is a nice tool but I give up here. It took me longer than I thought to get than done and I did not try any animation. I hope I won't forget next time or maybe I should write a kind of wrapper to produce the graphs I usually use. The tutorial here seems quite good Dashing D3js. You can find some beautiful graphs here: Mike Bostock.
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