I have created D3 globe.
I am stuck in issue, right now on click on plot, Map zoom in but it is not smooth zoom in.
I need to zoom in map with smooth transition.
http://projectsdemo.net/globe/v4/
globe.focus = function(d, k) { d3.selectAll('.globe').transition()
.duration(2000)
.tween("transform", function() {
var centroid = d3.geo.centroid(d);
var r = d3.interpolate(projection.rotate(), [-centroid[0], -centroid[1], 0]);
return function(t) {
//projection.rotate(r(t));
pathG.selectAll("path").attr("d", path);
var clipExtent = projection.clipExtent();
//projection.scale(1).translate([0, 0]).clipExtent(null);
//var b = path.bounds(d);
var minScale = 270,
maxScale = minScale * 5;
projection.rotate(r(t)).scale(Math.max(minScale, Math.min(maxScale, k)))
.translate([width / 2, height / 2])
.clipExtent(clipExtent);
}
});
Your rotate is transistioning because of this:
.rotate(r(t))
Where r is an interpolate function and t is the current step in the transition. It looks like your scale though:
.scale(Math.max(minScale, Math.min(maxScale, k)))
is just set to the same value at every step in the transition.
You need to set up a separate interpolate function for the scale:
var r = d3.interpolate(projection.rotate(), [-centroid[0], -centroid[1], 0]),
r2 = d3.interpolate(project.scale(), Math.max(minScale, Math.min(maxScale, k)));
Then, use this in your transition:
projection.rotate(r(t))
.scale(r2(t))
...
I am attempting to simplify a d3 map on zoom, and I am using this example as a starting point. However, when I replace the json file in the example with my own (http://weather-bell.com/res/nws_regions.topojson), I get a tiny upside-down little map.
Here is my jsfiddle: http://jsfiddle.net/8ejmH
code:
var width = 900,
height = 500;
var chesapeake = [-75.959, 38.250];
var scale,
translate,
visibleArea, // minimum area threshold for points inside viewport
invisibleArea; // minimum area threshold for points outside viewport
var simplify = d3.geo.transform({
point: function (x, y, z) {
if (z < visibleArea) return;
x = x * scale + translate[0];
y = y * scale + translate[1];
if (x >= 0 && x <= width && y >= 0 && y <= height || z >= invisibleArea) this.stream.point(x, y);
}
});
var zoom = d3.behavior.zoom()
.size([width, height])
.on("zoom", zoomed);
// This projection is baked into the TopoJSON file,
// but is used here to compute the desired zoom translate.
var projection = d3.geo.mercator().translate([0, 0])
var canvas = d3.select("#map").append("canvas")
.attr("width", width)
.attr("height", height);
var context = canvas.node().getContext("2d");
var path = d3.geo.path()
.projection(simplify)
.context(context);
d3.json("http://weather-bell.com/res/nws_regions.topojson", function (error, json) {
canvas.datum(topojson.mesh(topojson.presimplify(json)))
.call(zoomTo(chesapeake, 0.05).event)
.transition()
.duration(5000)
.each(jump);
});
function zoomTo(location, scale) {
var point = projection(location);
return zoom.translate([width / 2 - point[0] * scale, height / 2 - point[1] * scale])
.scale(scale);
}
function zoomed(d) {
translate = zoom.translate();
scale = zoom.scale();
visibleArea = 1 / scale / scale;
invisibleArea = 200 * visibleArea;
context.clearRect(0, 0, width, height);
context.beginPath();
path(d);
context.stroke();
}
function jump() {
var t = d3.select(this);
(function repeat() {
t = t.transition()
.call(zoomTo(chesapeake, 100).event)
.transition()
.call(zoomTo(chesapeake, 0.05).event)
.each("end", repeat);
})();
}
My guess is that the topojson file I am using already has the projection built in, so I should be using a null projection in d3.
The map renders properly if I do not use a projection at all: (http://jsfiddle.net/KQfrK/1/) - but then I cannot simplify on zoom.
I feel like I am missing something basic... perhaps I just need to somehow rotate and zoom into the map in my first fiddle.
Either way, I'd appreciate some help. Been struggling with this one.
Edit: I used QGIS to save the geojson file with a "EPSG:3857 - WGS 84 / Pseudo Mercator" projection.
However, when I convert this to topojson with the topojson command-line utility and then display it with D3 using the same code as above I get a blank screen.
Should I specify the projection within the topojson command-line utility? I tried to do that but I got an error message:
topojson --projection EPSG:3857 E:\gitstore\public\res\nws.geojson -o E:\gitstore\public\res\nws.topojson --id-property NAME
[SyntaxError: Unexpected token :]
The TopoJSON file doesn't have a projection built-in, you're simply using the default projection when you don't specify one (which is albersUsa, see the documentation). You can retrieve this projection by calling d3.geo.projection() without an argument. Then you can modify this projection in the usual way for zoom etc.
I set up this fiddle using the Mercator projection and I took a different approach to zooming in and out based on this block, which to me was a simpler approach. I have a feeling that there was an issue in the zoomTo function in the translate bit, but I could exactly what it was. So I replaced with the code below and included a recursive call:
function clicked(k) {
if (typeof k === 'undefined') k = 8;
g.transition()
.duration(5000)
.attr("transform", "translate(" + width / 2 + "," + height / 2 + ")scale(" + k + ")translate(" + -projection(chesapeake)[0] + "," + -projection(chesapeake)[1] + ")")
.each("end", function () {
(k === 8) ? k = 1 : k = 8;
clicked(k);
});
i'm trying to somehow sweep in a half-donut-chart, meaning starting with a blank screen the chart starts drawing at -90 degree (or 270) and performs a halfcircle until reaching 90 degree. the code looks like:
var width = 800;
var height = 400;
var radius = 300;
var grad=Math.PI/180;
var data = [30, 14, 4, 4, 5];
var color = d3.scale.category20();
var svg = d3.select("body").append("svg").attr("width", width).attr("height",
`height).append("g").attr("transform", "translate(" + radius*1.5 + "," + radius*1.5 +
")");
var arc = d3.svg.arc().innerRadius(radius - 100).outerRadius(radius - 20);
var pie = d3.layout.pie().sort(null);
svg.selectAll("path").data(pie(data)).enter().append("path").attr("d",
arc).attr("fill",
function(d, i) { return color(i); }).transition().duration(500).attrTween("d", sweep);
function sweep(a) {
var i = d3.interpolate({startAngle: -90*grad, endAngle: -90*grad},{startAngle: -90*grad, endAngle: 90*grad});
return function(t) {
return arc(i(t));
};
}
looking at several examples i managed to get the animation, however, i fail at binding (or converting) the data to the arc. my feeling is that there is only one path drawn and then it stops.
if i change the interpolation to start/end -90/90 and a, i get different colors but not all of them. adding the start/end-angle to the pie-var gives me a transition where a one-colored-arc is shown at the beginning and then the other parts slide in (which would be correct if there was no arc at the beginning - the proportions also seem a bit wrong). setting the initial color to white does not help because then everything stays white.
i'm afraid i'm missing an obvious point, but so far i'm stuck, maybe someone can point me in the right direction.
after quite some variations and tests it somehow started to work, using these to lines of code:
var pie = d3.layout.pie().sort(null).startAngle(-90*grad).endAngle(90*grad);
var i = d3.interpolate({startAngle: -90*grad, endAngle: -90*grad},a);
one final "problem" was that the height of the svg was too small and so some segments got cut off, so changing it to
var height = 800;
ended my search. thanks for any considerations.
A small typo on the
var svg = d3.select("body").append("svg").attr("width", width).attr("height", `height)
should be:
var svg = d3.select("body").append("svg").attr("width", width).attr("height", height)
Currently in d3 if you have a geoJSON object that you are going to draw you have to scale it and translate it in order to get it to the size that one wants and translate it in order to center it. This is a very tedious task of trial and error, and I was wondering if anyone knew a better way to obtain these values?
So for instance if I have this code
var path, vis, xy;
xy = d3.geo.mercator().scale(8500).translate([0, -1200]);
path = d3.geo.path().projection(xy);
vis = d3.select("#vis").append("svg:svg").attr("width", 960).attr("height", 600);
d3.json("../../data/ireland2.geojson", function(json) {
return vis.append("svg:g")
.attr("class", "tracts")
.selectAll("path")
.data(json.features).enter()
.append("svg:path")
.attr("d", path)
.attr("fill", "#85C3C0")
.attr("stroke", "#222");
});
How the hell do I obtain .scale(8500) and .translate([0, -1200]) without going little by little?
My answer is close to Jan van der Laan’s, but you can simplify things slightly because you don’t need to compute the geographic centroid; you only need the bounding box. And, by using an unscaled, untranslated unit projection, you can simplify the math.
The important part of the code is this:
// Create a unit projection.
var projection = d3.geo.albers()
.scale(1)
.translate([0, 0]);
// Create a path generator.
var path = d3.geo.path()
.projection(projection);
// Compute the bounds of a feature of interest, then derive scale & translate.
var b = path.bounds(state),
s = .95 / Math.max((b[1][0] - b[0][0]) / width, (b[1][1] - b[0][1]) / height),
t = [(width - s * (b[1][0] + b[0][0])) / 2, (height - s * (b[1][1] + b[0][1])) / 2];
// Update the projection to use computed scale & translate.
projection
.scale(s)
.translate(t);
After comping the feature’s bounding box in the unit projection, you can compute the appropriate scale by comparing the aspect ratio of the bounding box (b[1][0] - b[0][0] and b[1][1] - b[0][1]) to the aspect ratio of the canvas (width and height). In this case, I’ve also scaled the bounding box to 95% of the canvas, rather than 100%, so there’s a little extra room on the edges for strokes and surrounding features or padding.
Then you can compute the translate using the center of the bounding box ((b[1][0] + b[0][0]) / 2 and (b[1][1] + b[0][1]) / 2) and the center of the canvas (width / 2 and height / 2). Note that since the bounding box is in the unit projection’s coordinates, it must be multiplied by the scale (s).
For example, bl.ocks.org/4707858:
There’s a related question where which is how to zoom to a specific feature in a collection without adjusting the projection, i.e., combining the projection with a geometric transform to zoom in and out. That uses the same principles as above, but the math is slightly different because the geometric transform (the SVG "transform" attribute) is combined with the geographic projection.
For example, bl.ocks.org/4699541:
The following seems to do approximately what you want. The scaling seems to be ok. When applying it to my map there is a small offset. This small offset is probably caused because I use the translate command to center the map, while I should probably use the center command.
Create a projection and d3.geo.path
Calculate the bounds of the current projection
Use these bounds to calculate the scale and translation
Recreate the projection
In code:
var width = 300;
var height = 400;
var vis = d3.select("#vis").append("svg")
.attr("width", width).attr("height", height)
d3.json("nld.json", function(json) {
// create a first guess for the projection
var center = d3.geo.centroid(json)
var scale = 150;
var offset = [width/2, height/2];
var projection = d3.geo.mercator().scale(scale).center(center)
.translate(offset);
// create the path
var path = d3.geo.path().projection(projection);
// using the path determine the bounds of the current map and use
// these to determine better values for the scale and translation
var bounds = path.bounds(json);
var hscale = scale*width / (bounds[1][0] - bounds[0][0]);
var vscale = scale*height / (bounds[1][1] - bounds[0][1]);
var scale = (hscale < vscale) ? hscale : vscale;
var offset = [width - (bounds[0][0] + bounds[1][0])/2,
height - (bounds[0][1] + bounds[1][1])/2];
// new projection
projection = d3.geo.mercator().center(center)
.scale(scale).translate(offset);
path = path.projection(projection);
// add a rectangle to see the bound of the svg
vis.append("rect").attr('width', width).attr('height', height)
.style('stroke', 'black').style('fill', 'none');
vis.selectAll("path").data(json.features).enter().append("path")
.attr("d", path)
.style("fill", "red")
.style("stroke-width", "1")
.style("stroke", "black")
});
With d3 v4 or v5 its getting way easier!
var projection = d3.geoMercator().fitSize([width, height], geojson);
var path = d3.geoPath().projection(projection);
and finally
g.selectAll('path')
.data(geojson.features)
.enter()
.append('path')
.attr('d', path)
.style("fill", "red")
.style("stroke-width", "1")
.style("stroke", "black");
Enjoy, Cheers
I'm new to d3 - will try to explain how I understand it but I'm not sure I got everything right.
The secret is knowing that some methods will operate on the cartographic space (latitude,longitude) and others on the cartesian space (x,y on the screen). The cartographic space (our planet) is (almost) spherical, the cartesian space (screen) is flat - in order to map one over the other you need an algorithm, which is called projection. This space is too short to deep into the fascinating subject of projections and how they distort geographic features in order to turn spherical into plane; some are designed to conserve angles, others conserve distances and so on - there is always a compromise (Mike Bostock has a huge collection of examples).
In d3, the projection object has a center property/setter, given in map units:
projection.center([location])
If center is specified, sets the projection’s center to the specified location, a two-element array of longitude and latitude in degrees and returns the projection. If center is not specified, returns the current center which defaults to ⟨0°,0°⟩.
There is also the translation, given in pixels - where the projection center stands relative to the canvas:
projection.translate([point])
If point is specified, sets the projection’s translation offset to the specified two-element array [x, y] and returns the projection. If point is not specified, returns the current translation offset which defaults to [480, 250]. The translation offset determines the pixel coordinates of the projection’s center. The default translation offset places ⟨0°,0°⟩ at the center of a 960×500 area.
When I want to center a feature in the canvas, I like to set the projection center to the center of the feature bounding box - this works for me when using mercator (WGS 84, used in google maps) for my country (Brazil), never tested using other projections and hemispheres. You may have to make adjustments for other situations, but if you nail these basic principles you will be fine.
For example, given a projection and path:
var projection = d3.geo.mercator()
.scale(1);
var path = d3.geo.path()
.projection(projection);
The bounds method from path returns the bounding box in pixels. Use it to find the correct scale, comparing the size in pixels with the size in map units (0.95 gives you a 5% margin over the best fit for width or height). Basic geometry here, calculating the rectangle width/height given diagonally opposed corners:
var b = path.bounds(feature),
s = 0.9 / Math.max(
(b[1][0] - b[0][0]) / width,
(b[1][1] - b[0][1]) / height
);
projection.scale(s);
Use the d3.geo.bounds method to find the bounding box in map units:
b = d3.geo.bounds(feature);
Set the center of the projection to the center of the bounding box:
projection.center([(b[1][0]+b[0][0])/2, (b[1][1]+b[0][1])/2]);
Use the translate method to move the center of the map to the center of the canvas:
projection.translate([width/2, height/2]);
By now you should have the feature in the center of the map zoomed with a 5% margin.
There is a center() method you can use that accepts a lat/lon pair.
From what I understand, translate() is only used for literally moving the pixels of the map. I am not sure how to determine what scale is.
In addition to Center a map in d3 given a geoJSON object, note that you may prefer fitExtent() over fitSize() if you want to specify a padding around the bounds of your object. fitSize() automatically sets this padding to 0.
I was looking around on the Internet for a fuss-free way to center my map, and got inspired by Jan van der Laan and mbostock's answer. Here's an easier way using jQuery if you are using a container for the svg. I created a border of 95% for padding/borders etc.
var width = $("#container").width() * 0.95,
height = $("#container").width() * 0.95 / 1.9 //using height() doesn't work since there's nothing inside
var projection = d3.geo.mercator().translate([width / 2, height / 2]).scale(width);
var path = d3.geo.path().projection(projection);
var svg = d3.select("#container").append("svg").attr("width", width).attr("height", height);
If you looking for exact scaling, this answer won't work for you. But if like me, you wish to display a map that centralizes in a container, this should be enough. I was trying to display the mercator map and found that this method was useful in centralizing my map, and I could easily cut off the Antarctic portion since I didn't need it.
To pan/zoom the map you should look at overlaying the SVG on Leaflet. That will be a lot easier than transforming the SVG. See this example http://bost.ocks.org/mike/leaflet/ and then How to change the map center in leaflet
With mbostocks' answer, and Herb Caudill's comment, I started running into issues with Alaska since I was using a mercator projection. I should note that for my own purposes, I am trying to project and center US States. I found that I had to marry the two answers with Jan van der Laan answer with following exception for polygons that overlap hemispheres (polygons that end up with a absolute value for East - West that is greater than 1):
set up a simple projection in mercator:
projection = d3.geo.mercator().scale(1).translate([0,0]);
create the path:
path = d3.geo.path().projection(projection);
3.set up my bounds:
var bounds = path.bounds(topoJson),
dx = Math.abs(bounds[1][0] - bounds[0][0]),
dy = Math.abs(bounds[1][1] - bounds[0][1]),
x = (bounds[1][0] + bounds[0][0]),
y = (bounds[1][1] + bounds[0][1]);
4.Add exception for Alaska and states that overlap the hemispheres:
if(dx > 1){
var center = d3.geo.centroid(topojson.feature(json, json.objects[topoObj]));
scale = height / dy * 0.85;
console.log(scale);
projection = projection
.scale(scale)
.center(center)
.translate([ width/2, height/2]);
}else{
scale = 0.85 / Math.max( dx / width, dy / height );
offset = [ (width - scale * x)/2 , (height - scale * y)/2];
// new projection
projection = projection
.scale(scale)
.translate(offset);
}
I hope this helps.
For people who want to adjust verticaly et horizontaly, here is the solution :
var width = 300;
var height = 400;
var vis = d3.select("#vis").append("svg")
.attr("width", width).attr("height", height)
d3.json("nld.json", function(json) {
// create a first guess for the projection
var center = d3.geo.centroid(json)
var scale = 150;
var offset = [width/2, height/2];
var projection = d3.geo.mercator().scale(scale).center(center)
.translate(offset);
// create the path
var path = d3.geo.path().projection(projection);
// using the path determine the bounds of the current map and use
// these to determine better values for the scale and translation
var bounds = path.bounds(json);
var hscale = scale*width / (bounds[1][0] - bounds[0][0]);
var vscale = scale*height / (bounds[1][1] - bounds[0][1]);
var scale = (hscale < vscale) ? hscale : vscale;
var offset = [width - (bounds[0][0] + bounds[1][0])/2,
height - (bounds[0][1] + bounds[1][1])/2];
// new projection
projection = d3.geo.mercator().center(center)
.scale(scale).translate(offset);
path = path.projection(projection);
// adjust projection
var bounds = path.bounds(json);
offset[0] = offset[0] + (width - bounds[1][0] - bounds[0][0]) / 2;
offset[1] = offset[1] + (height - bounds[1][1] - bounds[0][1]) / 2;
projection = d3.geo.mercator().center(center)
.scale(scale).translate(offset);
path = path.projection(projection);
// add a rectangle to see the bound of the svg
vis.append("rect").attr('width', width).attr('height', height)
.style('stroke', 'black').style('fill', 'none');
vis.selectAll("path").data(json.features).enter().append("path")
.attr("d", path)
.style("fill", "red")
.style("stroke-width", "1")
.style("stroke", "black")
});
How I centered a Topojson, where I needed to pull out the feature:
var projection = d3.geo.albersUsa();
var path = d3.geo.path()
.projection(projection);
var tracts = topojson.feature(mapdata, mapdata.objects.tx_counties);
projection
.scale(1)
.translate([0, 0]);
var b = path.bounds(tracts),
s = .95 / Math.max((b[1][0] - b[0][0]) / width, (b[1][1] - b[0][1]) / height),
t = [(width - s * (b[1][0] + b[0][0])) / 2, (height - s * (b[1][1] + b[0][1])) / 2];
projection
.scale(s)
.translate(t);
svg.append("path")
.datum(topojson.feature(mapdata, mapdata.objects.tx_counties))
.attr("d", path)