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SAT scores sluggish?
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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 |
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<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> |
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