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Thinking with Joins

Thinking with Joins
Say you’re making a basic scatterplot using D3, and you need to create some SVG circle elements to visualize your data. You may be surprised to discover that D3 has no primitive for creating multiple DOM elements. Wait, WAT? Sure, there’s the append method, which you can use to create a single element. svg.append("circle") .attr("cx", d.x) .attr("cy", d.y) .attr("r", 2.5); But that’s just a single circle, and you want many circles: one for each data point. svg.selectAll("circle") .data(data) .enter().append("circle") .attr("cx", function(d) { return d.x; }) .attr("cy", function(d) { return d.y; }) .attr("r", 2.5); This code does exactly what you need: it creates a circle element for each data point, using the x and y data properties for positioning. Here’s the deal. Data points joined to existing elements produce the update (inner) selection. Now we can unravel the mysterious enter-append sequence through the data join: But why all the trouble? Likewise, to shrink-out:

http://bost.ocks.org/mike/join/

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D3 Tutorials <div id="js_warning"><strong>JavaScript is turned off, so this page won&rsquo;t be very interactive.</strong> Switch JavaScript back on in your web browser for the full experience.</div> These tutorials have been expanded into a book, Interactive Data Visualization for the Web, published by O’Reilly in March 2013. Purchase the ebook and print editions from O’Reilly. A free, online version includes interactive examples. Election site part 1: Basics with Knockout.js, Bootstrap and d3.js This article shows how you can use knockout.js, Twitter's Bootstrap and d3.js together to create a javascript application that creates visually pleasing graphics and diagrams to your users. This is complete client side solution that only communicates with REST to the server. This is part 1 of a series of articles discussing these concepts. In this first article we'll look at setting up the basic application and we'll demonstrate how to use knockout.js, bootstrap and d3.js. It's a bit too much to show all the javascript in this article. You can find the demo for this version (with a couple more features) at this url: So if you want to see the some of the util functions I use look at the javascript used in that example.

d3: scales, and color. In protovis, scales were super-useful in just about everything. That much hasn’t changed in d3, even though d3.scale is a bit different from pv.Scale. (do note that d3.scale is in lowercase for starters). Scales: the main idea Simply put: scales transform a number in a certain interval (called the domain) into a number in another interval (called the range). For instance, let’s suppose you know your data is always over 20 and always below 80. Adding an SVG Element Basic Example In the last example you added a p HTML element to the DOM. In this example, you will use D3.js to add an SVG element to a basic webpage. Per our previous SVG examples , you will add an SVG circle to the webpage.

How Selections Work Any sufficiently advanced technology is indistinguishable from magic. –Arthur C. Clarke In the past I have presented simplified descriptions of D3’s selections, providing only enough detail to get started. This article takes a more comprehensive approach; rather than saying how to use selections, I will explain how selections are implemented. This may take longer to read, but it should dispel any magic and help you master data-driven documents. Documentation Learn the basics of D3 with this introductory tutorial, covering the core concepts of selections and data binding. Read me first! Using the example of a no-frills, static bar chart, this guide describes the core D3 concepts, including selections, functional properties, and scales.

Eurozone crisis This graphic attempts to visualise how the Eurozone crisis developed over time. Seven key indicators are shown for the Eurozone and each of the original 12 Eurozone members. The outer radius of the ring shows the maximum within the Eurozone for a given month and the inner radius the minimum. The thick blue line shows the median. SVG and Handlebars JS Templates I’ve been working with Handlebars JS for a while and wanted to use templating to generate portions of SVG. If you read my last post on SVG and JavaScript, a proper namespace is the key to the SVG castle. So I needed a way to get the output from my Handlebars template to be seen as proper SVG. This is the handlebars template I’m working with. This template is for a single character from my Auto Andy project. First thing to do is create a SVG Element.

From Shapefile to GeoJSON - Jim Vallandingham A method for editing, merging, simplifying, and converting Shapefiles to GeoJSON D3.js supports cartographic visualizations by being able to display lines, polygons, and other geometry objects . It uses GeoJSON as the storage format for this type of visualization.

Selections · mbostock/d3 Wiki Wiki ▸ API Reference ▸ Core ▸ Selections A selection is an array of elements pulled from the current document. D3 uses CSS3 to select elements. For example, you can select by tag ("div"), class (".awesome"), unique identifier ("#foo"), attribute ("[color=red]"), or containment ("parent child"). Selectors can also be intersected (".this.that" for logical AND) or unioned (".this, .that" for logical OR).

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