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DRY Bar Chart
license: gpl-3.0

A variation of the example bar chart using a slightly more D.R.Y. style. The visual encoding is represented by two functions and their composition:

  • The value accessor returns the value (or property) to encode for a given data object.
  • The scale maps this value to a visual display encoding, such as a pixel position.
  • The map function represents the composition valuescale, mapping from data to display.

Inspired by Andrew Winterman’s post, Tooling for the Lazy Programmer: DRYing up D3.

letter frequency
A .08167
B .01492
C .02780
D .04253
E .12702
F .02288
G .02022
H .06094
I .06973
J .00153
K .00747
L .04025
M .02517
N .06749
O .07507
P .01929
Q .00098
R .05987
S .06333
T .09056
U .02758
V .01037
W .02465
X .00150
Y .01971
Z .00074
<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
font: 10px sans-serif;
}
.axis path,
.axis line {
fill: none;
stroke: #000;
shape-rendering: crispEdges;
}
.bar {
fill: steelblue;
}
.x.axis path {
display: none;
}
</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>
var margin = {top: 20, right: 20, bottom: 30, left: 40},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom;
var formatPercent = d3.format(".0%");
var xValue = function(d) { return d.letter; }, // data -> value
xScale = d3.scale.ordinal().rangeRoundBands([0, width], .1), // value -> display
xMap = function(d) { return xScale(xValue(d)); }, // data -> display
xAxis = d3.svg.axis().scale(xScale).orient("bottom");
var yValue = function(d) { return d.frequency; }, // data -> value
yScale = d3.scale.linear().range([height, 0]), // value -> display
yMap = function(d) { return yScale(yValue(d)); }, // data -> display
yAxis = d3.svg.axis().scale(yScale).orient("left").tickFormat(formatPercent);
var svg = d3.select("body").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
d3.tsv("data.tsv", type, function(error, data) {
xScale.domain(data.map(xValue));
yScale.domain([0, d3.max(data, yValue)]);
svg.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")")
.call(xAxis);
svg.append("g")
.attr("class", "y axis")
.call(yAxis)
.append("text")
.attr("transform", "rotate(-90)")
.attr("y", 6)
.attr("dy", ".71em")
.style("text-anchor", "end")
.text("Frequency");
svg.selectAll(".bar")
.data(data)
.enter().append("rect")
.attr("class", "bar")
.attr("x", xMap)
.attr("width", xScale.rangeBand)
.attr("y", yMap)
.attr("height", function(d) { return height - yMap(d); });
});
function type(d) {
d.frequency = +d.frequency;
return d;
}
</script>
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