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36_map_zoom_event.html
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36_map_zoom_event.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>D3: Zoom events</title>
<script type="text/javascript" src="d3.js"></script>
<style type="text/css">
body {
background-color: gray;
}
svg {
background-color: black;
}
</style>
</head>
<body>
<div id="mapContainer"></div>
<button id="zoomIn">Zoom In</button>
<button id="zoomOut">Zoom Out</button>
<script type="text/javascript">
//Globals for use later
var countries;
var cities;
//Year of CO2 data to map
var year = "2010";
//Width and height
var w = 500;
var h = 300;
//Define map projection
var projection = d3.geo.mercator()
.center([ 0, 40 ])
.translate([ w/2, h/2 ])
.scale([ w/7 ]);
//Define path generator
var path = d3.geo.path()
.projection(projection);
//
//Configure zoom behavior
//
var maxZoomIn = w*2;
var maxZoomOut = w/7;
var zoom = d3.behavior.zoom()
.translate( projection.translate() )
.scale( projection.scale() )
.scaleExtent([ maxZoomOut, maxZoomIn ])
//Defines the on("zoom") event! That is, what
//to do on double-click or mousewheel roll.
.on("zoom", function(d) {
//Get the translate and scale values from this event
var t = d3.event.translate;
var s = d3.event.scale;
//Update the zoom and projection objects with these
zoom.translate(t);
projection.translate(t).scale(s);
//Recalculate paths (given new t and s values)
countries.attr("d", path);
//Recalculate cities (same idea)
cities.attr("cx", function(d) {
return projection([d.longitude, d.latitude])[0];
})
.attr("cy", function(d) {
return projection([d.longitude, d.latitude])[1];
});
});
//Define zoom in and out functions that we can call easily later
var zoomIn = function() {
var newScale = Math.min(projection.scale() * 2, maxZoomIn);
zoomTo(newScale);
};
var zoomOut = function() {
var newScale = Math.max(projection.scale() / 2, maxZoomOut);
zoomTo(newScale);
};
//Define zoomTo function to which we can pass a new scale value
zoomTo = function(newScale) {
var t = projection.translate(),
s = projection.scale();
t[0] -= w / 2;
t[0] *= newScale / s;
t[0] += w / 2;
t[1] -= h * 0.55;
t[1] *= newScale / s;
t[1] += h * 0.55;
zoom.translate(t).scale(newScale);
projection.translate(t).scale(newScale);
//Finally, transition paths and circles into place
countries.transition()
.ease("linear")
.delay(50)
.duration(500)
.attr("d", path);
cities.transition()
.ease("linear")
.duration(500)
.attr("cx", function(d) {
return projection([d.longitude, d.latitude])[0];
})
.attr("cy", function(d) {
return projection([d.longitude, d.latitude])[1];
});
};
//Assign zoom button behavior
d3.select("#zoomIn")
.on("click", function() {
zoomIn();
});
d3.select("#zoomOut")
.on("click", function() {
zoomOut();
});
//Define quantize scale to sort data values into buckets of color
//Colors by Cynthia Brewer (colorbrewer2.org), YlOrRd
var color = d3.scale.quantize()
.range([ "#ffffb2", "#fecc5c", "#fd8d3c", "#f03b20", "#bd0026" ]);
//Create SVG
var svg = d3.select("#mapContainer")
.append("svg")
.attr("width", w)
.attr("height", h);
//Load in CO2 data
d3.csv("data/co2/co2_emissions.csv", function(data) {
//Set input domain for color scale
color.domain([
d3.min(data, function(d) { return +d[year]; }),
d3.max(data, function(d) { return +d[year]; })
]);
//Load in GeoJSON data
d3.json("data/geo/mapshaper_output.json", function(json) {
//Merge the CO2 data and GeoJSON into a single array
//
//Loop through once for each CO2 data value
for (var i = 0; i < data.length; i++) {
//Grab country name
var dataCountryCode = data[i].countryCode;
//Grab data value, and convert from string to float
var dataValue = +data[i][year];
//Find the corresponding country inside the GeoJSON
for (var j = 0; j < json.features.length; j++) {
//We'll check the official ISO country code
var jsonCountryCode = json.features[j].properties.iso_a3;
if (dataCountryCode == jsonCountryCode) {
//Copy the data value into the GeoJSON
json.features[j].properties.co2 = dataValue;
//Stop looking through the JSON
break;
}
}
}
//Create a group to contain all the country paths.
//This is primarily to catch zoom events, even when
//the mouse is positioned over the ocean.
var countriesGroup = svg.append("g")
.attr("id", "countriesGroup")
.call(zoom); //Bind zoom listener to the countries group
//Create a rectangle in the background.
//This is purely to ensure this group fills the whole
//SVG image, so mousewheel events are caught.
countriesGroup.append("rect")
.attr("x", 0)
.attr("y", 0)
.attr("width", w)
.attr("height", h);
//Bind data and create one path per GeoJSON feature
countries = countriesGroup.selectAll("path")
.data(json.features)
.enter()
.append("path")
.attr("d", path)
.style("fill", function(d) {
//Get data value
var value = d.properties.co2;
if (value) {
//If value exists…
return color(value);
} else {
//If value is undefined…
return "#ccc";
}
});
//Load in cities data
d3.csv("data/cities/cities.csv", function(data) {
cities = svg.selectAll("circle")
.data(data)
.enter()
.append("circle")
.attr("cx", function(d) {
return projection([d.longitude, d.latitude])[0];
})
.attr("cy", function(d) {
return projection([d.longitude, d.latitude])[1];
})
.attr("r", function(d) {
return Math.sqrt(+d.population / w * 0.001);
})
.style("fill", "blue")
.style("opacity", 0.75);
});
}); //End d3.json()
}); //End d3.csv()
</script>
</body>
</html>