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11-data-transition-with-key.html
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11-data-transition-with-key.html
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<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
<title>Data transition with key</title>
<script src="https://d3js.org/d3.v4.min.js"></script>
<style type="text/css">
.bar {
fill: steelblue;
stroke: none;
}
.highlight {
fill: red;
}
</style>
</head>
<body>
<script type="text/javascript">
//Define our random-number generator function
var _id_ = 0;
function generate() {
return {
index: _id_++,
value: 1000 * Math.random()
};
}
//Generate random data to use for the chart
var data = d3.range(100).map(generate);
//Set variables for desired size of chart
var w = 900,
h = 100,
bw = 9;
//Define a scale for y axis values
var yScale = d3.scaleLinear()
.domain([0, d3.max(data, function(d) { return d.value; })])
.range([0, 100]);
//Define a key function to uniquely identify data values
var key = function(d) {
return d.index;
};
//Select the <body> and create a new SVG element
var svg = d3.select("body").append("svg")
.attr("width", w)
.attr("height", h);
//Create a series of 'rect' elements within the SVG
svg.selectAll("rect.bar")
.data(data, function(d) {
return d.index; // <-- Reference key function within data join
})
.enter()
.append("rect")
.attr("class", "bar")
.attr("x", function(d, i) {
return i * bw;
})
.attr("width", bw - 1)
.attr("y", function(d) {
return h - yScale(d.value);
})
.attr("height", function(d) {
return yScale(d.value);
})
.on("mouseover", function(d) {
d3.select(this).classed("highlight", true);
})
.on("mouseout", function(d) {
d3.select(this).classed("highlight", false);
});
//Define a new function that updates all data
function update() {
data.shift();
data.push(generate());
//Re-select bars
var bars = svg.selectAll("rect.bar")
.data(data, key); // <-- …while using key function!
//Add a new rect for the incoming data (one new value)
bars.enter()
.append("rect") //Note the the lines below are exactly the same as above
.attr("class", "bar") //from when we first created all the bars initially.
.attr("x", w) // <-- Put it just outside the frame of the SVG element
.attr("width", bw - 1)
.attr("y", function(d) {
return h - yScale(d.value);
})
.attr("height", function(d) {
return yScale(d.value);
})
.on("mouseover", function(d) {
d3.select(this).classed("highlight", true);
})
.on("mouseout", function(d) {
d3.select(this).classed("highlight", false);
});
//Re-position bars along x-axis with animation
//'bars' now contains both the enter and update sets
bars.transition()
.duration(500)
.attr("x", function(d, i) {
return i * bw;
});
}
//Execute this update function every two seconds
d3.interval(update, 2000);
</script>
</body>
</html>