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Reusable D3 column chart that supports negative values

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README.md
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column-chart.js
JavaScript
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function columnChart() {
var margin = {top: 30, right: 10, bottom: 50, left: 50},
width = 420,
height = 420,
xRoundBands = 0.2,
xValue = function(d) { return d[0]; },
yValue = function(d) { return d[1]; },
xScale = d3.scale.ordinal(),
yScale = d3.scale.linear(),
yAxis = d3.svg.axis().scale(yScale).orient("left"),
xAxis = d3.svg.axis().scale(xScale);
 
function chart(selection) {
selection.each(function(data) {
 
// Convert data to standard representation greedily;
// this is needed for nondeterministic accessors.
data = data.map(function(d, i) {
return [xValue.call(data, d, i), yValue.call(data, d, i)];
});
// Update the x-scale.
xScale
.domain(data.map(function(d) { return d[0];} ))
.rangeRoundBands([0, width - margin.left - margin.right], xRoundBands);
 
// Update the y-scale.
yScale
.domain(d3.extent(data.map(function(d) { return d[1];} )))
.range([height - margin.top - margin.bottom, 0])
.nice();
 
// Select the svg element, if it exists.
var svg = d3.select(this).selectAll("svg").data([data]);
 
// Otherwise, create the skeletal chart.
var gEnter = svg.enter().append("svg").append("g");
gEnter.append("g").attr("class", "bars");
gEnter.append("g").attr("class", "y axis");
gEnter.append("g").attr("class", "x axis");
gEnter.append("g").attr("class", "x axis zero");
 
// Update the outer dimensions.
svg .attr("width", width)
.attr("height", height);
 
// Update the inner dimensions.
var g = svg.select("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
 
// Update the bars.
var bar = svg.select(".bars").selectAll(".bar").data(data);
bar.enter().append("rect");
bar.exit().remove();
bar .attr("class", function(d, i) { return d[1] < 0 ? "bar negative" : "bar positive"; })
.attr("x", function(d) { return X(d); })
.attr("y", function(d, i) { return d[1] < 0 ? Y0() : Y(d); })
.attr("width", xScale.rangeBand())
.attr("height", function(d, i) { return Math.abs( Y(d) - Y0() ); });
 
// x axis at the bottom of the chart
g.select(".x.axis")
.attr("transform", "translate(0," + (height - margin.top - margin.bottom) + ")")
.call(xAxis.orient("bottom"));
// zero line
g.select(".x.axis.zero")
.attr("transform", "translate(0," + Y0() + ")")
.call(xAxis.tickFormat("").tickSize(0));
// Update the y-axis.
g.select(".y.axis")
.call(yAxis);
});
}
 
 
// The x-accessor for the path generator; xScale ∘ xValue.
function X(d) {
return xScale(d[0]);
}
 
function Y0() {
return yScale(0);
}
 
// The x-accessor for the path generator; yScale ∘ yValue.
function Y(d) {
return yScale(d[1]);
}
 
chart.margin = function(_) {
if (!arguments.length) return margin;
margin = _;
return chart;
};
 
chart.width = function(_) {
if (!arguments.length) return width;
width = _;
return chart;
};
 
chart.height = function(_) {
if (!arguments.length) return height;
height = _;
return chart;
};
 
chart.x = function(_) {
if (!arguments.length) return xValue;
xValue = _;
return chart;
};
 
chart.y = function(_) {
if (!arguments.length) return yValue;
yValue = _;
return chart;
};
 
return chart;
}
index.html
HTML
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<!DOCTYPE html>
<meta charset="utf-8">
<html>
<head>
<script src="http://d3js.org/d3.v2.min.js?2.10.0"></script>
<script type="text/javascript" src="../d3.v2.js" charset="utf-8" ></script>
<script type="text/javascript" src="column-chart.js"></script>
<style>
 
.chart rect {
stroke: white;
fill-opacity: .6;
fill: steelblue;
 
}
.bar.positive {
fill: steelblue;
}
 
.bar.negative {
fill: brown;
}
 
.axis text {
font: 10px sans-serif;
}
 
.axis path, .axis line {
fill: none;
stroke: #000;
shape-rendering: crispEdges;
}
 
 
</style>
</head>
<body>
<div id="example"></div>
 
<script>
 
var data = [["A",0.012], ["B",-0.025], ["C",0.008], ["D",0.023], ["E",-0.009], ["F", 0.005]];
 
 
d3.select("#example")
.datum(data)
.call(columnChart()
.width(960)
.height(500)
.x(function(d, i) { return d[0]; })
.y(function(d, i) { return d[1]; }));
 
</script>
 
 
</body>
</html>

This is a fantastic time saver! Thanks! Is it possible to modify ticks and tick format? I'm new to D3, still getting my head around how to get at these.

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