tomgp/data.csv

## data.csv

          
            expenditure per pupil
            sat scores
            year

            
              3600
              840
              80

            
              3650
              845
              81

            
              3700
              850
              82

            
              3800
              840
              83

            
              4000
              850
              84

            
              4100
              860
              85

            
              4250
              880
              86

            
              4400
              900
              87

            
              4495
              905
              88

## index.html
<html>
<head>
	<title>Dual Y Axes</title>
	<script src="http://d3js.org/d3.v3.min.js" charset="utf-8"></script>
	<style type="text/css">
		body{
			font-family: sans-serif;
		}
		.domain{
			fill:none;
			stroke:#000;
			shape-rendering:crispEdges;
		}

		.plot{
			fill:none;
			stroke-width:2;
		}

		.cost-scale .tick{
			fill:#F00;
		}

		.sat-scale .tick{
			fill:#00F;
		}

		.hidden{
			display:none;
		}
		.notes{
			max-width: 600px;
		}
	</style>
</head>
<body>

<h1 class="active">SAT scores remain sluggish despite funding increase <a href="#" data-satDomain="800,1200" data-costDomain="2800,4800">(OR...)</a></h1>
<h1 class="hidden">SAT scores soar despite sluggish funding <a href="#" data-satDomain="800,910" data-costDomain="0,20000">(OR...)</a></h1>
<div class="chart"></div>

<div class="notes">
<p>Why dual axis charts are a bad idea.</p>

<p>Click on the &quot;OR&quot; in the headline to see the same data drawn with different scales.</p>

<p>An example taken from <a href="http://www.sagepub.com/gray/Website%20material/Journals/er_wainer.pdf">Howard Wainer's Understanding Graphs and Tables</a> (figs&nbsp;6&nbsp;&amp;&nbsp;7) for more on the problems of dual y-axes see <a href="http://www.perceptualedge.com/articles/visual_business_intelligence/dual-scaled_axes.pdf">Steven Few's Dual-Scaled Axes in Graphs
Are They Ever the Best Solution?</a></p></div>


</body>
<script type="text/javascript">
var height=500, width=800,
	margin={ top:50, left:150, bottom:70, right:100 },
	axisGap = 5,
	plotWidth = width-(margin.left+margin.right),
	plotHeight = height-(margin.top+margin.bottom);

var satDomain = [0,1000];
var costDomain = [0,5000];
var data =[];

var container = d3.select('.chart')
	.append('svg')
		.attr({
			width:width,
			height:height
		})
	.append('g')
		.attr({
			'transform':'translate(' + margin.left + ',' + margin.top + ')'
		});

container.append('g').attr({
	'class':'sat-scale',
	'transform':'translate('+ (plotWidth + axisGap) +',0)'
});

container.append('g').attr({
	'class':'cost-scale',
	'transform':'translate('+ (- axisGap) +',0)'
});

container.append('g').attr({
	'class':'time-scale',
	'transform':'translate(0,' + (plotHeight + axisGap) + ')'
});

var plot = container.append('g').attr({
	'class':'plot'
});

plot.append('path').attr({
	'class':'sat-line'
});

plot.append('path').attr({
	'class':'cost-line'
});

var labels = container.append('g')
	.attr('class','labels')

labels.append('text')
	.attr({
		fill:'#F00',
		'transform':'translate(0,'+(-axisGap*4)+')',
		'text-anchor':'end'
	}).text('Expenditure/ pupil $');

labels.append('text')
	.attr({
		fill:'#00F',
		'transform':'translate(' + plotWidth + ','+(-axisGap*4)+')'
	}).text('SAT score');

labels.append('text')
	.attr({
		'transform':'translate(' + plotWidth/2 + ','+(plotHeight + axisGap*10)+')'
	}).text('year');

function getDomains(){
	var d = d3.select('h1.active a').node().dataset;
	satDomain = d.satdomain.split(',').map(function(d){return Number(d); });
	costDomain = d.costdomain.split(',').map(function(d){return Number(d); });
}

function drawChart(){
	var costScale = d3.scale.linear()
		.range([plotHeight, 0])
		.domain(costDomain),

	satScale = d3.scale.linear()
		.range([plotHeight, 0])
		.domain(satDomain),

	timeScale = d3.scale.linear()
		.range([0,plotWidth])
		.domain(d3.extent(data, function(d){ return d.year; })),

	leftAxis = d3.svg.axis()
		.scale(costScale)
		.orient('left'),

	rightAxis = d3.svg.axis()
		.scale(satScale)
		.orient('right'),

	timeAxis = d3.svg.axis()
		.scale(timeScale)
		.orient('bottom'),

	costLine = d3.svg.line()
	    .x(function(d) { return timeScale(d.year); })
	    .y(function(d) { return costScale(d['expenditure per pupil']); });

	satLine = d3.svg.line()
	    .x(function(d) { return timeScale(d.year); })
	    .y(function(d) { return satScale(d['sat scores']); });

	d3.select( '.sat-scale' ).call( rightAxis );
	d3.select( '.cost-scale' ).call( leftAxis );
	d3.select( '.time-scale' ).call( timeAxis );

	d3.select( '.cost-line' )
      .datum(data)
      	  .transition()
	      .attr({
	      	'd': costLine,
	      	'stroke':'#F00',
	      	'stroke-width': 2
	      });

    d3.select(' .sat-line ')
      .datum(data)
	      .transition()
	      .attr({
	      	'd': satLine,
	      	'stroke':'#00F',
	      	'stroke-width': 2
	      });
}

d3.selectAll('a').on('click',function(d){
	console.log(this);
	//toggle h1s
	d3.selectAll('h1')
		.attr({
			'class':function(){
				if (d3.select(this).classed('hidden')){
					return 'active';
				}
				return 'hidden';
			}
		})

	getDomains();
	drawChart();
})

d3.csv('data.csv', function(d){
	data = d;
	getDomains();
	drawChart();
})

</script>
</html>
expenditure per pupil	sat scores	year
3600	840	80
3650	845	81
3700	850	82
3800	840	83
4000	850	84
4100	860	85
4250	880	86
4400	900	87
4495	905	88
	<html>
	<head>
	<title>Dual Y Axes</title>
	<script src="http://d3js.org/d3.v3.min.js" charset="utf-8"></script>
	<style type="text/css">
	body{
	font-family: sans-serif;
	}
	.domain{
	fill:none;
	stroke:#000;
	shape-rendering:crispEdges;
	}

	.plot{
	fill:none;
	stroke-width:2;
	}

	.cost-scale .tick{
	fill:#F00;
	}

	.sat-scale .tick{
	fill:#00F;
	}

	.hidden{
	display:none;
	}
	.notes{
	max-width: 600px;
	}
	</style>
	</head>
	<body>

	<h1 class="active">SAT scores remain sluggish despite funding increase <a href="#" data-satDomain="800,1200" data-costDomain="2800,4800">(OR...)</a></h1>
	<h1 class="hidden">SAT scores soar despite sluggish funding <a href="#" data-satDomain="800,910" data-costDomain="0,20000">(OR...)</a></h1>
	<div class="chart"></div>

	<div class="notes">
	<p>Why dual axis charts are a bad idea.</p>

	<p>Click on the "OR" in the headline to see the same data drawn with different scales.</p>

	<p>An example taken from <a href="http://www.sagepub.com/gray/Website%20material/Journals/er_wainer.pdf">Howard Wainer's Understanding Graphs and Tables</a> (figs 6 & 7) for more on the problems of dual y-axes see <a href="http://www.perceptualedge.com/articles/visual_business_intelligence/dual-scaled_axes.pdf">Steven Few's Dual-Scaled Axes in Graphs
	Are They Ever the Best Solution?</a></p></div>


	</body>
	<script type="text/javascript">
	var height=500, width=800,
	margin={ top:50, left:150, bottom:70, right:100 },
	axisGap = 5,
	plotWidth = width-(margin.left+margin.right),
	plotHeight = height-(margin.top+margin.bottom);

	var satDomain = [0,1000];
	var costDomain = [0,5000];
	var data =[];

	var container = d3.select('.chart')
	.append('svg')
	.attr({
	width:width,
	height:height
	})
	.append('g')
	.attr({
	'transform':'translate(' + margin.left + ',' + margin.top + ')'
	});

	container.append('g').attr({
	'class':'sat-scale',
	'transform':'translate('+ (plotWidth + axisGap) +',0)'
	});

	container.append('g').attr({
	'class':'cost-scale',
	'transform':'translate('+ (- axisGap) +',0)'
	});

	container.append('g').attr({
	'class':'time-scale',
	'transform':'translate(0,' + (plotHeight + axisGap) + ')'
	});

	var plot = container.append('g').attr({
	'class':'plot'
	});

	plot.append('path').attr({
	'class':'sat-line'
	});

	plot.append('path').attr({
	'class':'cost-line'
	});

	var labels = container.append('g')
	.attr('class','labels')

	labels.append('text')
	.attr({
	fill:'#F00',
	'transform':'translate(0,'+(-axisGap*4)+')',
	'text-anchor':'end'
	}).text('Expenditure/ pupil $');

	labels.append('text')
	.attr({
	fill:'#00F',
	'transform':'translate(' + plotWidth + ','+(-axisGap*4)+')'
	}).text('SAT score');

	labels.append('text')
	.attr({
	'transform':'translate(' + plotWidth/2 + ','+(plotHeight + axisGap*10)+')'
	}).text('year');

	function getDomains(){
	var d = d3.select('h1.active a').node().dataset;
	satDomain = d.satdomain.split(',').map(function(d){return Number(d); });
	costDomain = d.costdomain.split(',').map(function(d){return Number(d); });
	}

	function drawChart(){
	var costScale = d3.scale.linear()
	.range([plotHeight, 0])
	.domain(costDomain),

	satScale = d3.scale.linear()
	.range([plotHeight, 0])
	.domain(satDomain),

	timeScale = d3.scale.linear()
	.range([0,plotWidth])
	.domain(d3.extent(data, function(d){ return d.year; })),

	leftAxis = d3.svg.axis()
	.scale(costScale)
	.orient('left'),

	rightAxis = d3.svg.axis()
	.scale(satScale)
	.orient('right'),

	timeAxis = d3.svg.axis()
	.scale(timeScale)
	.orient('bottom'),

	costLine = d3.svg.line()
	.x(function(d) { return timeScale(d.year); })
	.y(function(d) { return costScale(d['expenditure per pupil']); });

	satLine = d3.svg.line()
	.x(function(d) { return timeScale(d.year); })
	.y(function(d) { return satScale(d['sat scores']); });

	d3.select( '.sat-scale' ).call( rightAxis );
	d3.select( '.cost-scale' ).call( leftAxis );
	d3.select( '.time-scale' ).call( timeAxis );

	d3.select( '.cost-line' )
	.datum(data)
	.transition()
	.attr({
	'd': costLine,
	'stroke':'#F00',
	'stroke-width': 2
	});

	d3.select(' .sat-line ')
	.datum(data)
	.transition()
	.attr({
	'd': satLine,
	'stroke':'#00F',
	'stroke-width': 2
	});
	}

	d3.selectAll('a').on('click',function(d){
	console.log(this);
	//toggle h1s
	d3.selectAll('h1')
	.attr({
	'class':function(){
	if (d3.select(this).classed('hidden')){
	return 'active';
	}
	return 'hidden';
	}
	})

	getDomains();
	drawChart();
	})

	d3.csv('data.csv', function(d){
	data = d;
	getDomains();
	drawChart();
	})

	</script>
	</html>