Created
August 19, 2014 19:45
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Plotting a bell (Gaussian) curve in d3
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<!DOCTYPE html> | |
<html> | |
<head> | |
<meta charset="utf-8"> | |
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> | |
<title>Normal Plot</title> | |
<meta name="description" content=""> | |
<script src="http://d3js.org/d3.v3.min.js" charset="utf-8"></script> | |
<style type="text/css"> | |
body { | |
font: 10px sans-serif; | |
} | |
.axis path, | |
.axis line { | |
fill: none; | |
stroke: #000; | |
shape-rendering: crispEdges; | |
} | |
/*.x.axis path { | |
display: none; | |
}*/ | |
.line { | |
fill: none; | |
stroke: steelblue; | |
stroke-width: 1.5px; | |
} | |
</style> | |
</head> | |
<body> | |
</body> | |
<script type="text/javascript"> | |
//setting up empty data array | |
var data = []; | |
getData(); // popuate data | |
// line chart based on http://bl.ocks.org/mbostock/3883245 | |
var margin = { | |
top: 20, | |
right: 20, | |
bottom: 30, | |
left: 50 | |
}, | |
width = 960 - margin.left - margin.right, | |
height = 500 - margin.top - margin.bottom; | |
var x = d3.scale.linear() | |
.range([0, width]); | |
var y = d3.scale.linear() | |
.range([height, 0]); | |
var xAxis = d3.svg.axis() | |
.scale(x) | |
.orient("bottom"); | |
var yAxis = d3.svg.axis() | |
.scale(y) | |
.orient("left"); | |
var line = d3.svg.line() | |
.x(function(d) { | |
return x(d.q); | |
}) | |
.y(function(d) { | |
return y(d.p); | |
}); | |
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 + ")"); | |
x.domain(d3.extent(data, function(d) { | |
return d.q; | |
})); | |
y.domain(d3.extent(data, function(d) { | |
return d.p; | |
})); | |
svg.append("g") | |
.attr("class", "x axis") | |
.attr("transform", "translate(0," + height + ")") | |
.call(xAxis); | |
svg.append("g") | |
.attr("class", "y axis") | |
.call(yAxis); | |
svg.append("path") | |
.datum(data) | |
.attr("class", "line") | |
.attr("d", line); | |
function getData() { | |
// loop to populate data array with | |
// probabily - quantile pairs | |
for (var i = 0; i < 100000; i++) { | |
q = normal() // calc random draw from normal dist | |
p = gaussian(q) // calc prob of rand draw | |
el = { | |
"q": q, | |
"p": p | |
} | |
data.push(el) | |
}; | |
// need to sort for plotting | |
//https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort | |
data.sort(function(x, y) { | |
return x.q - y.q; | |
}); | |
} | |
// from http://bl.ocks.org/mbostock/4349187 | |
// Sample from a normal distribution with mean 0, stddev 1. | |
function normal() { | |
var x = 0, | |
y = 0, | |
rds, c; | |
do { | |
x = Math.random() * 2 - 1; | |
y = Math.random() * 2 - 1; | |
rds = x * x + y * y; | |
} while (rds == 0 || rds > 1); | |
c = Math.sqrt(-2 * Math.log(rds) / rds); // Box-Muller transform | |
return x * c; // throw away extra sample y * c | |
} | |
//taken from Jason Davies science library | |
// https://github.com/jasondavies/science.js/ | |
function gaussian(x) { | |
var gaussianConstant = 1 / Math.sqrt(2 * Math.PI), | |
mean = 0, | |
sigma = 1; | |
x = (x - mean) / sigma; | |
return gaussianConstant * Math.exp(-.5 * x * x) / sigma; | |
}; | |
</script> | |
</html> |
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