Module 6: Tree Ring Line Chart

<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="utf-8">
		<title>Tree Ring Widths for Northern and Southern Hemispheres, by Year</title>
		<script type="text/javascript" src="https://d3js.org/d3.v3.js"></script>
		<style type="text/css">
			
			body {
				background-color: white;
				font-family: Helvetica, Arial, sans-serif;
			}

h1 {
				font-size: 24px;
				margin: 0;
			}

p {
				font-size: 14px;
				margin: 10px 0 0 0;
			}

svg {
				background-color: white;
			}

circle:hover {
				fill: orange;
			}
			
			.axis path,
			.axis line {
				fill: none;
				stroke: black;
				shape-rendering: crispEdges;
			}
			
			.axis text {
				font-family: sans-serif;
				font-size: 11px;
			}

</style>
	</head>
	<body>

<h1>Tree Ring Widths (in mm) for Northern and Southern Hemispheres, by Year</h1>

<p>Tree ring widths measure the growth of trees over time; larger widths indicate a better growing season. Data are not available for all years. Source: <a href="https://www.ncdc.noaa.gov/paleo/treering.html">National Centers for Environmental Information</a>, 2014</p>

//Dimensions and padding
			var w = 1000;
			var h = 600;
			var padding = [ 20, 10, 50, 100 ];  //Top, right, bottom, left

//Set up date formatting and years
			var dateFormat = d3.time.format("%Y");

//Set up scales
			var xScale = d3.time.scale()
								.range([ padding[3], w - padding[1] - padding[3] ]);
			
			var yScale = d3.scale.linear()
								.range([ padding[0], h - padding[2] ]);

//Configure axis generators
			var xAxis = d3.svg.axis()
							.scale(xScale)
							.orient("bottom")
							.ticks(12)
							.tickFormat(function(d) {
								return dateFormat(d);
							});

var yAxis = d3.svg.axis()
							.scale(yScale)
							.orient("left");

//Configure line generator
			var line = d3.svg.line()
				.x(function(d) {
					return xScale(dateFormat.parse(d.Year));
				})
				.y(function(d) {
					return yScale(+d.TreeRingWidth);
				});

//Create the empty SVG image
			var svg = d3.select("body")
						.append("svg")
						.attr("width", w)
						.attr("height", h);

//Load USA data
			d3.csv("TreeRingWidth_Northern.csv", function(NorthernData) {

//Load China data
				d3.csv("TreeRingWidth_Southern.csv", function(SouthernData) {

//Create a new array that contains both the
					//northern and southern hemisphere data, merged into one
					var mergedData = NorthernData.concat(SouthernData);
					//console.log(mergedData);

//Use the newly merged data to determine the
					//min and max values, for setting scale domains
					xScale.domain([ 
						d3.min(mergedData, function(d) {
							return dateFormat.parse(d.Year);
						}),
						d3.max(mergedData, function(d) {
							return dateFormat.parse(d.Year);
						})
					]);

yScale.domain([ 
						d3.max(mergedData, function(d) {
							return +d.TreeRingWidth;
						}),
						860
					]);

//Lines
					//
					// Note data is wrapped in another array, so all its
					// values are bound to a single element (the line!)
					//
					svg.data([ NorthernData ])
						.append("path")
						.attr("class", "line northern")
						.attr("d", line)
						.attr("fill", "none")
						.attr("stroke", "steelblue")
						.attr("stroke-width", 2);

svg.data([ SouthernData ])
						.append("path")
						.attr("class", "line southern")
						.attr("d", line)
						.attr("fill", "none")
						.attr("stroke", "red")
						.attr("stroke-width", 2);

//Axes
					svg.append("g")
						.attr("class", "x axis")
						.attr("transform", "translate(0," + (h - padding[2]) + ")")
						.call(xAxis);

svg.append("g")
						.attr("class", "y axis")
						.attr("transform", "translate(" + (padding[3]) + ",0)")
						.call(yAxis);

});
				//End Southern data load function

});
			//End Northern data load function

</script>

</body>
</html>

Modified http://d3js.org/d3.v3.js to a secure url

https://d3js.org/d3.v3.js