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Farthest feasible point filter
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<html> | |
<head> | |
<meta charset="utf-8"> | |
<link href="main.css" rel="stylesheet"> | |
</head> | |
<body> | |
<script src="http://d3js.org/d3.v3.min.js"></script> | |
<script src="main.js"></script> | |
</body> | |
</html> |
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.axis path, | |
.axis line { | |
fill: none; | |
stroke: #ccc; | |
shape-rendering: crispEdges; | |
} |
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var margin = {top: 50, right: 20, bottom: 50, left: 40}, | |
width = 960 - margin.left - margin.right, | |
height = 300 - margin.top - margin.bottom | |
var pointsNumber = 45 | |
var Δ = 0.1 | |
var x = d3.scale.linear() | |
.domain([0, pointsNumber]) | |
.range([0, width]) | |
var y = d3.scale.linear() | |
.domain([0, 1]) | |
.range([height, 0]) | |
var yAxis = d3.svg.axis() | |
.scale(y) | |
.orient("left") | |
var svg = d3.select("body").append("svg") | |
.attr("width", width + margin.left + margin.right) | |
.attr("height", height + margin.top + margin.bottom) | |
var area = svg | |
.append("g") | |
.attr("transform", "translate(" + margin.left + "," + margin.top + ")") | |
area.append("g") | |
.attr("class", "axis") | |
.call(yAxis) | |
var areaGroup = area.append('g') | |
var ffpGroup = area.append('g') | |
var ε = 1e-6 | |
function filterData(d, Δ) { | |
d = d.slice() | |
var start = 0, | |
result = [], | |
trendBoundaries = [Infinity, -Infinity], | |
currentPointBoundaries = [], | |
currentPointTrend, | |
farthestFeasible = 0, | |
lower = 0, | |
upper = 1, | |
pushPoint = function () { result.push({ x: farthestFeasible, y: d[farthestFeasible] }) } | |
pushPoint() | |
while (farthestFeasible < d.length - 1) { | |
for (var i = start; i < d.length; i++) { | |
currentPointBoundaries = [ | |
(d[i] - d[start] + Δ) / (i - start), | |
(d[i] - d[start] - Δ) / (i - start) | |
] | |
if (trendBoundaries[upper] < currentPointBoundaries[upper] + ε) { | |
trendBoundaries[upper] = currentPointBoundaries[upper] | |
} | |
if (currentPointBoundaries[lower] < trendBoundaries[lower] + ε) { | |
trendBoundaries[lower] = currentPointBoundaries[lower] | |
} | |
currentPointTrend = (d[i] - d[start]) / (i - start) | |
if (trendBoundaries[upper] < currentPointTrend + ε && currentPointTrend < trendBoundaries[lower] + ε) { | |
farthestFeasible = i | |
} else if (trendBoundaries[lower] < trendBoundaries[upper] + ε) { | |
trendBoundaries = [Infinity, -Infinity] | |
i = start = farthestFeasible | |
pushPoint() | |
} | |
} | |
trendBoundaries = [Infinity, -Infinity] | |
start = farthestFeasible | |
pushPoint() | |
} | |
return result | |
} | |
var i = 0 | |
var currentValue = Math.random() | |
var values = [] | |
var limit = d3.scale.linear().clamp(true) | |
setInterval(function() { | |
if (i < pointsNumber) { | |
currentValue = limit(currentValue + .3 * Math.random() - .15 + .01 * Math.cos(i * 5)) | |
values.push(currentValue) | |
var circles = areaGroup.selectAll('circle') | |
.data(values) | |
circles.exit().remove() | |
circles | |
.enter().append('circle') | |
.attr('cx', function(d, i) { return x(i) }) | |
.attr('cy', function(d) { return y(d) }) | |
.attr('r', 0) | |
.attr('fill', '#aaa') | |
.transition() | |
.attr('r', 1.5) | |
var data = filterData(values, Δ) | |
var filteredDots = ffpGroup.selectAll('circle') | |
.data(data, function (d) { return d.x + " " + d.y }) | |
filteredDots.exit().remove() | |
filteredDots | |
.enter().append('circle') | |
.attr('cx', function(d) { return x(d.x) }) | |
.attr('cy', function(d) { return y(d.y) }) | |
.attr('fill', '#000') | |
.attr('r', 0) | |
.transition() | |
.attr('r', 1.5) | |
var boundaries = [] | |
function offsetLine (line, offset) { | |
return [{x: line[0].x, y: line[0].y + offset}, {x: line[1].x, y: line[1].y + offset}] | |
} | |
d3.pairs(data).forEach(function(d) { | |
boundaries.push(d) | |
boundaries.push(offsetLine(d, Δ)) | |
boundaries.push(offsetLine(d, -Δ)) | |
}) | |
var lines = areaGroup.selectAll('line') | |
.data(boundaries, function (d) { return d[0].x + " " + d[0].y + " " + d[1].x + " " + d[1].y }) | |
lines.exit().remove() | |
lines.enter().append('line') | |
.attr('stroke', '#ccc') | |
.attr('x1', function(d) { return x(d[0].x) }) | |
.attr('y1', function(d) { return y(d[0].y) }) | |
.attr('x2', function(d) { return x(d[1].x) }) | |
.attr('y2', function(d) { return y(d[1].y) }) | |
i++ | |
} | |
}, 500) |
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