D3: Adding new data to column chart

Example of adding extra data to a column chart and leveraging of transitions.

Exercise from the “Interactive Data Visualization for the Web, Second Edition” by Scott Murray. Forked from the example: 09_25_adding_values.html

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<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
  <p><button>Click on this button to add a new data value to the chart!</button></p>
			
		<script type="text/javascript">

//Width and height
			var w = 900;
			var h = 450;
			
			var dataset = [ 5, 10, 13, 19, 21, 25, 22, 18, 15, 13,
							11, 12, 15, 20, 18, 17, 16, 18, 23, 25 ];
			
			var xScale = d3.scaleBand()
							.domain(d3.range(dataset.length))
							.rangeRound([0, w])
							.paddingInner(0.05);

var yScale = d3.scaleLinear()
							.domain([0, d3.max(dataset)])
							.range([0, h]);
			
			//Create SVG element
			var svg = d3.select("body")
						.append("svg")
						.attr("width", w)
						.attr("height", h);

//Create bars
			svg.selectAll("rect")
			   .data(dataset)
			   .enter()
			   .append("rect")
			   .attr("x", function(d, i) {
			   		return xScale(i);
			   })
			   .attr("y", function(d) {
			   		return h - yScale(d);
			   })
			   .attr("width", xScale.bandwidth())
			   .attr("height", function(d) {
			   		return yScale(d);
			   })
			   .attr("fill", function(d) {
					return "rgb(0, 0, " + Math.round(d * 10) + ")";
			   });

//Create labels
			svg.selectAll("text")
			   .data(dataset)
			   .enter()
			   .append("text")
			   .text(function(d) {
			   		return d;
			   })
			   .attr("text-anchor", "middle")
			   .attr("x", function(d, i) {
			   		return xScale(i) + xScale.bandwidth() / 2;
			   })
			   .attr("y", function(d) {
			   		return h - yScale(d) + 14;
			   })
			   .attr("font-family", "sans-serif")
			   .attr("font-size", "11px")
			   .attr("fill", "white");

//On click, update with new data			
			d3.select("p")
				.on("click", function() {

//Add one new value to dataset
					var maxValue = 25;
					var newNumber = Math.floor(Math.random() * maxValue);	//New random integer (0-24)
					dataset.push(newNumber);			 			 		//Add new number to array
					
					//Update scale domains
					xScale.domain(d3.range(dataset.length));	//Recalibrate the x scale domain, given the new length of dataset
					yScale.domain([0, d3.max(dataset)]);		//Recalibrate the y scale domain, given the new max value in dataset

//Select…
					var bars = svg.selectAll("rect")			//Select all bars
						.data(dataset);	//Re-bind data to existing bars, return the 'update' selection
														//'bars' is now the update selection					
					//Enter…
					bars.enter()	//References the enter selection (a subset of the update selection)
						.append("rect")	//Creates a new rect
						.attr("x", w)		//Initial x position of the rect beyond the right edge of SVG
						.attr("y", function(d) {	//Sets the y value, based on the updated yScale
							return h - yScale(d);
						})
						.attr("width", xScale.bandwidth())	//Sets the width value, based on the updated xScale
						.attr("height", function(d) {			//Sets the height value, based on the updated yScale
							return yScale(d);
						})
						.attr("fill", function(d) {				//Sets the fill value
							return "rgb(0, 0, " + Math.round(d * 10) + ")";
						})
						.merge(bars)							//Merges the enter selection with the update selection
						.transition()							//Initiate a transition on all elements in the update selection (all rects)
						.duration(500)
						.attr("x", function(d, i) {				//Set new x position, based on the updated xScale
							return xScale(i);
						})
						.attr("y", function(d) {				//Set new y position, based on the updated yScale
							return h - yScale(d);
						})
						.attr("width", xScale.bandwidth())		//Set new width value, based on the updated xScale
						.attr("height", function(d) {			//Set new height value, based on the updated yScale
							return yScale(d);
						});

//Update all labels
					var labels = svg.selectAll("text")
											 		.data(dataset);
					
					labels.enter()
					   .append("text")
					   .text(function(d) {
					   		return d;
					   })
					   .attr("text-anchor", "middle")
					   .attr("font-family", "sans-serif")
					   .attr("font-size", "11px")
					   .attr("fill", function(d) {
								if (d < 0.07 * maxValue){	return "black"	}
			   				else {	return "white"	}
			   			})
					   .attr("x", function(d, i) {
							return w + xScale.bandwidth() / 2;
					   })
					   .attr("y", function(d) {
							if (d < 0.07 * maxValue){	return h - yScale(d) - 7	}
			   			else {	return h - yScale(d) + 14;	}
					   })
					   .merge(labels)
					   .transition()
					   .duration(500)
					   .attr("x", function(d, i) { //Set new x position, based on the updated xScale
							return xScale(i) + xScale.bandwidth() / 2;
						})

});
      </script>
</body>

https://d3js.org/d3.v4.min.js