31:T565,map = { // You'll often see Leaflet examples initializing a map like L.map('map'), // which tells the library to look for a div with the id 'map' on the page. // In Observable, we instead create a div from scratch in this cell (called "map") let container = DOM.element('div', { style: `width:${width}px;height:${width/1.6}px` }); // This component utilizes "yield" which pauses the execution of this code block // returns the value of container back to the notebook which allows the // div to be placed on the page. This is important, because Leaflet uses // the div's .offsetWidth and .offsetHeight (used to get current size of the div) // to size the map. If I were to only return the container at the end of this method, // Leaflet might get the wrong idea about the map's size. yield container; // Now we create a map object and add a layer to it. let map = L.map(container).setView([49.2527, -123.1207], 11.5); // initializes the map, sets zoom & coordinates let osmLayer = L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', { attribution: '© OpenStreetMap contributors' }).addTo(map); //This adds the tile layer to the map. The map dynamically loads tiles based on current view the experience smooth and seamless. Make sure to add attribution to your map. }32:T452,VanAreasMap = { let container = DOM.element('div', { style: `width:${width}px;height:${width/1.6}px` }); yield container; let map = L.map(container);// Did not set view because we are using "fit bounds" to get the polygons to determine this let osmLayer = L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', { attribution: '© OpenStreetMap contributors' }).addTo(map); let VanAreasLayer = L.geoJson(VanAreas, { //instantiates a new geoJson layer using built in geoJson handling weight: 2, //Attributes of polygons including the weight of boundaries and colors of map. color: "#432", }).bindPopup(function (Layer) { //binds a popup when clicking on each polygon to access underlying data return Layer.feature.properties.NAME; }).addTo(map); //Adds the layer to the map. map.fitBounds(VanAreasLayer.getBounds()); //finds bounds of polygon and automatically gets map view to fit (useful for interaction and not having to 'cook' the map zoom and coordinates as in map instantiation }33:T877,Dots = { //define our map size const width = 600 const height = 400 // This is a Observables specific convenience method which creates an SVG in the DOM. const svg = d3.select(DOM.svg(width, height)) //projection this projects out points into space and fits the viewport based on const projection = d3.geoMercator().fitExtent([[50,50], [width-50, height-50]], Wcities) ; const points = svg.selectAll('circle')//Selects all circles (haven't been created yet, I know its confusing) .data(Wcities.features) //loads the data we need - In this case our flat array of objects of features .join('circle') //creates a circle for each element in the array .attr("fill", "steelblue") // colors it blue .attr("cx", d => projection(d.geometry.coordinates)[0]) // forEach element takes the coordinates and *projects* .attr("cy", d => projection(d.geometry.coordinates)[1]) // then we index this array for the long(x) and lat(y) .attr("r", 5) //radius of the circle .on('mouseover', function() { //function to add mouseover event d3.select(this).transition() //D3 selects the object we have moused over in order to perform operations on it .duration('150') //how long we are transitioning between the two states (works like keyframes) .attr("fill", "red") //change the fill .attr('r', 10) //change radius }) .on('mouseout', function() { //reverse the action based on when we mouse off the the circle d3.select(this).transition() .duration('150') .attr("fill", "steelblue") .attr('r', 5) }); //Add text description for each city const text = svg.selectAll('text') .data(Wcities.features) .join('text') .attr("font-size", '9') .attr("dy", 3) //shift on y-axis to align .attr("x", d => projection(d.geometry.coordinates)[0]+5) //Offset to make it visible .attr("y", d => projection(d.geometry.coordinates)[1]) .text(d => d.properties.Name) //Set teh text according to data return svg.node(); }34:Tb58,WesternCanadianCities = { let container = DOM.element('div', { style: `width:${width}px;height:${width/1.6}px` }); yield container; let map = L.map(container).setView([53.2527, -123.1207], 5).fitBounds(L.geoJson(Wcities).getBounds()); let osmLayer = L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', { attribution: '© OpenStreetMap contributors' }).addTo(map); //initialize svg to add to map L.svg({clickable:true}).addTo(map)// we have to make the svg layer clickable const overlay = d3.select(map.getPanes().overlayPane) const svg = overlay.select('svg').attr("pointer-events", "auto") const Dots = svg.selectAll('circle') .attr("class", "Dots") .data(Wcities.features) .join('circle') .attr("id", "dotties") .attr("fill", "steelblue") .attr("stroke", "black") //Leaflet has to take control of projecting points. Here we are feeding the latitude and longitude coordinates to //leaflet so that it can project them on the coordinates of the view. Notice, we have to reverse lat and lon. //Finally, the returned conversion produces an x and y point. We have to select the the desired one using .x or .y .attr("cx", d => map.latLngToLayerPoint([d.geometry.coordinates[1],d.geometry.coordinates[0]]).x) .attr("cy", d => map.latLngToLayerPoint([d.geometry.coordinates[1],d.geometry.coordinates[0]]).y) .attr("r", 5) .on('mouseover', function() { //function to add mouseover event d3.select(this).transition() //D3 selects the object we have moused over in order to perform operations on it .duration('150') //how long we are transitioning between the two states (works like keyframes) .attr("fill", "red") //change the fill .attr('r', 10) //change radius }) .on('mouseout', function() { //reverse the action based on when we mouse off the the circle d3.select(this).transition() .duration('150') .attr("fill", "steelblue") .attr('r', 5) }); const update = () => Dots .attr("cx", d => map.latLngToLayerPoint([d.geometry.coordinates[1],d.geometry.coordinates[0]]).x) .attr("cy", d => map.latLngToLayerPoint([d.geometry.coordinates[1],d.geometry.coordinates[0]]).y) map.on("zoomend", update) }35:T766,D3VanAreasMap = { let container = DOM.element('div', { style: `width:${width}px;height:${width/1.6}px` }); yield container; let map = L.map(container).setView([49.2527, -123.1207], 11.5); let osmLayer = L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', { attribution: '© OpenStreetMap contributors' }).addTo(map); //initialize svg to add to map L.svg({clickable:true}).addTo(map) // we have to make the svg layer clickable //Create selection using D3 const overlay = d3.select(map.getPanes().overlayPane) const svg = overlay.select('svg').attr("pointer-events", "auto") // create a group that is hidden during zooming const g = svg.append('g').attr('class', 'leaflet-zoom-hide') // Use Leaflets projection API for drawing svg path (creates a stream of projected points) const projectPoint = function(x, y) { const point = map.latLngToLayerPoint(new L.LatLng(y, x)) this.stream.point(point.x, point.y) } // Use d3's custom geo transform method to implement the above const projection = d3.geoTransform({point: projectPoint}) // creates geopath from projected points (SVG) const pathCreator = d3.geoPath().projection(projection) const areaPaths = g.selectAll('path') .data(VanAreas.features) .join('path') .attr('fill-opacity', 0.3) .attr('stroke', 'black') .attr("z-index", 3000) .attr('stroke-width', 2.5) .on("mouseover", function(d){ d3.select(this).attr("fill", "red") }) .on("mouseout", function(d){ d3.select(this).attr("fill", "black") }) // Function to place svg based on zoom const onZoom = () => areaPaths.attr('d', pathCreator) // initialize positioning onZoom() // reset whenever map is moved map.on('zoomend', onZoom) }36:[{"id":"50886802bef6525bb0c59e392b3744a58d6b11da68399a2738366370d9924ed41c1017d9c1c2358798c1327ea891c22545fd5be224cdf1961e3c4f36d33ac950","href":"https://static.observableusercontent.com/files/50886802bef6525bb0c59e392b3744a58d6b11da68399a2738366370d9924ed41c1017d9c1c2358798c1327ea891c22545fd5be224cdf1961e3c4f36d33ac950","name":"map.geojson","type":"application/geo+json","lastModified":1574200929190.189,"size":980},{"id":"e8a1c62e61765cd84ab67631082775bd53395bcd4f1a6d6fd19f74e236194b9e9606ab4b04114ed5024d04dfffa5a7e1685f0cdf4707636dc571a8e6eef584a8","href":"https://static.observableusercontent.com/files/e8a1c62e61765cd84ab67631082775bd53395bcd4f1a6d6fd19f74e236194b9e9606ab4b04114ed5024d04dfffa5a7e1685f0cdf4707636dc571a8e6eef584a8","name":"VancouverAreaSize.json","type":"application/json","lastModified":1574200929190.189,"size":52857},{"id":"8ef4099dcffc981f20c5cc8429be6f7d1c8bd99039aab8730a7e279e57af0896388ff67f9f1b3eaed9db97efc61545464292d53108541ea6af231b5531328bd4","href":"https://static.observableusercontent.com/files/8ef4099dcffc981f20c5cc8429be6f7d1c8bd99039aab8730a7e279e57af0896388ff67f9f1b3eaed9db97efc61545464292d53108541ea6af231b5531328bd4","name":"feds.json","type":"application/json","lastModified":1574200929190.189,"size":880675}] 2f:{"title":"Intro to leaflet+d3 + interactivity","cells":[{"id":0,"value":"md`# Intro to leaflet+d3 + interactivity`","pinned":false,"hidden":false,"mode":"ojs"},{"id":17,"value":"md`# Leaflet\n\n[Leaflet](http://leafletjs.com/) is a library for embedding maps on websites. Up until now, we have used vega which plots spatial files on a blank canvas and has limited interaction. There are no background tiles which have to change based on zoom level and what part of the map is in view. In order to utilize a map that supports zooming and panning (like in google maps), we have to use a tile map server that provides these data. Leaflet automatically allows users to connect to tile map servers and other GIS data servers to create maps where user can zoom, pan, and add interactive layers on top. Including a leaflet map on observable has its own unique requirements:\n\n## Including Leaflet\n\n1. First, include the Leaflet JavaScript with \\`require()\\` to pull it from https://unpkg.com\n2. Also include Leaflet's required CSS as a link tag, also pulling from unpkg.`","pinned":false,"hidden":false,"mode":"ojs"},{"id":21,"value":"L = require('leaflet@1.2.0')","pinned":true,"hidden":false,"mode":"ojs"},{"id":23,"value":"html``","pinned":true,"hidden":false,"mode":"ojs"},{"id":172,"value":"md` ## Preparing data for leaflet\nLeaflet unfortunately does not allow you to use TopoJson files. You will have to convert them to geoJson for use in leaflet. There are many ways to do this, but a quick an easy way is to use [mapshaper.org](http://mapshaper.org/). Download the TopoJson below and open mapshaper. Here, I am using a new feature in observable [file attachment](https://observablehq.com/@observablehq/file-attachments), which allows you to upload files to be hosted in your notebook as long as they are below 15 MB.`","pinned":false,"hidden":false,"mode":"ojs"},{"id":181,"value":"ElectoralDistricts = FileAttachment(\"feds.json\").json()","pinned":true,"hidden":false,"mode":"ojs"},{"id":208,"value":"md` **Challenge:** convert canadian electoral districts to geojson using mapshaper.org`","pinned":false,"hidden":false,"mode":"ojs"},{"id":25,"value":"md` ## Creating a base map\nHere we create a simple that uses openstreetmaps as a tile server. You can find other base tile maps that suit your needs [here](https://leaflet-extras.github.io/leaflet-providers/preview/). `","pinned":false,"hidden":false,"mode":"ojs"},{"id":33,"value":"$31","pinned":true,"hidden":false,"mode":"ojs"},{"id":212,"value":"md ` **Challenge:** create a leaflet map of vancouver using a different basemap`","pinned":false,"hidden":false,"mode":"ojs"},{"id":46,"value":"md` ## Adding Data to Map\nLet's take out vancouver neighbourhoods and add them as a layer to leaflet. `","pinned":false,"hidden":false,"mode":"ojs"},{"id":58,"value":"VanAreas = FileAttachment(\"VancouverAreaSize.json\").json()","pinned":true,"hidden":false,"mode":"ojs"},{"id":64,"value":"$32","pinned":true,"hidden":false,"mode":"ojs"},{"id":215,"value":"md` **Challenge:** Create map of Canada's electoral districts using the file you converted into GeoJson previously`","pinned":false,"hidden":false,"mode":"ojs"},{"id":167,"value":"md` ## D3\nWe are now moving into [D3](https://d3js.org/). D3 is a large library that takes a long time to master, and has lot of idiosyncracies with how it functions. You will notice that there are limits to what you can do in Vega-Lite, and that is also true in Vega (which we have not spent much time on). Instead, we are going to jump straight into D3. Vega-lite and Vega are especially limited in their ability to perform various mapping operations. As you have seen, from the example above, one of those is being able to bring in map tiles and support zooming and panning across many zoom levels and have a relatively seamless experience while doing so. D3.js gives you the flexibility to implement the features that you feel you may need (although, the development time to do so may take longer than you may want). To introduce d3.js, we will be making a very simple dot map.`","pinned":false,"hidden":false,"mode":"ojs"},{"id":225,"value":"Wcities = FileAttachment(\"map.geojson\").json()","pinned":false,"hidden":false,"mode":"ojs"},{"id":232,"value":"$33","pinned":true,"hidden":false,"mode":"ojs"},{"id":305,"value":"md`This is great, but we have no base map. We could draw a base map in d3, but what is much better is to combine d3 with leaflet. This allows us all of the functionality of leaflet (without having to reinvent the wheel), along with the flexibility of D3.js to let us do what we like with it.`","pinned":false,"hidden":false,"mode":"ojs"},{"id":310,"value":"$34","pinned":true,"hidden":false,"mode":"ojs"},{"id":88,"value":"md`\nHere is another map using polygons. This example gets a bit more complicated. You are free to look at it and play with it. We are going to be covering more complex topics next tutorial.`","pinned":false,"hidden":false,"mode":"ojs"},{"id":115,"value":"$35","pinned":true,"hidden":false,"mode":"ojs"},{"id":470,"value":"md` To make the svg layer interactive we have to turn on pointer events for it in a custom css style`","pinned":false,"hidden":false,"mode":"ojs"},{"id":452,"value":"html`