D3.js: How to handle dynamic JSON Data | Hacker News Reader

D3.js: How to handle dynamic JSON Data

pothibo.com

167 pointspothibo26 comments

I'm just getting started with d3 myself, and I found this ebook, which is free online, to be a great tutorial for all of things mentioned in the OP's post, but in greater detail:

http://chimera.labs.oreilly.com/books/1230000000345/index.ht...

D3.js is a beast, but it can be tamed. It took me a month to wrap my head around what was going on, but once you figure out what's happening, the data visualizations you can create are amazing.

It's definitely the best book there is, but you're going to need to practice a lot and read a lot of articles to really wrap your head around d3.js.

If I could recommend a way to learn d3.js:

1. Read Scott's book (and code the examples).

2. Think of some simple charts you want to make (and code them).

3. Use #d3.js@freenode, Stack Overflow, and see if some of the articles at http://www.d3noob.org/ fit what you're trying to do.

4. Go to http://bl.ocks.org/mbostock, be inspired, fork the code, and apply it to your own idea.

Repeat #3.

Ideally, find some kind of community where you can discuss with and help each other out regularly, but I don't really know of such a place, and it can be hard to find someone to do this with physically outside Paris, Berlin, NYC, and SF.

I haven't been to any, but from the google group it looks like London also has quality meetups pretty regularly.

This is my favorite getting started on d3 tutorial: http://www.jeromecukier.net/blog/2013/03/05/d3-tutorial-at-s...

It's peculiar how there are a billion beginner-level articles on d3.js, but the people who get stuck usually need something between that and intermediate.

If someone considers writing a d3.js tutorial, I'd urge them to use a real example, since this is where people realize they should use features like line.defined(), figure out how to implement gridlines yourself, and so on.

As great as d3.js, it's really hard to dive into the official wiki/docs as well as hit them for help.

Wow, I've been using d3 for almost a year now and I didn't know that line.defined() existed.

I've made lots of stuff with d3 and never needed grid lines or dealt with undefined line values, so my 'getting your hands dirty' tutorial would probably deal with totally different issues than what would be useful for you. At a certain point, you just have to buckle down and read the documentation - a quick peak at the page for svg.axis shows how to get grid lines extremely easily (http://bl.ocks.org/mbostock/4323929).

Hanging out on the stackoverflow tag is also super helpful. I either know how to answer a question and get some internet points or Lars responds within an hour and I learn something new.

The d3.js google group is a good place to discuss intermediate/advanced topics and get some help when you're hopelessly stuck. https://groups.google.com/forum/#!forum/d3-js

Should I learn d3 or three.js or raw canvas?

I would give different answers depending on what you're trying to do.

Do you have some data you want to visualize in an interactive way? Maybe try D3.js

Do you want to make 3d models or video games? THREE.js

Do you want to do custom 2D drawings that aren't suited to the previous two? Maybe raw canvas is for you.

Did you mean: > Should I learn d3 or three.js or raw canvas first?

Find some comparison tutorials between canvas and either of these, to see just how much more labor-intensive canvas tends to be. Then maybe make a decision as to what to dive deep into first.

I would also check out the readings and resources linked on http://www.cs171.org

D3.js was a major focus of the course, and lectures from previous years are published for free, as well. It was really well structured.

Whoa, I purchased this book when it was in pre release and even then hath ought it was wonderful. Not only is it he best walk through of D3 so far written, it's one of the best explanations of HTML and JavaScript, even for relative newbies.

That it is free is a huge act of generosity.

I highly recommend reading Mike Bostock's tutorials:

https://github.com/mbostock/d3/wiki/Tutorials

Especially, the first four: Introduction, Three Little Circles, Thinking with Joins, How Selections Work.

These articles explain the basic concepts of d3.

Then learn by doing is the best way to go. For example, http://vida.io/explore

The tutorial that helped me figure out how to use dynamic JSON data was the one on Path Transitions: http://bost.ocks.org/mike/path/

Not to be too much of a pedant, but the phrase

> SVG has an opposite y-coordinate system (0 is on top, height() is at the bottom).

struck me as silly, since that's how the coordinate systems of nearly all computer graphics systems work, not really opposite....

Yes, but it's the opposite of math-convention, which many of us have been taught since ~6th grade.

Anyone who has done any amount of work with computer graphics knows that this is the norm; but a new programmer, or just one that hasn't worked with graphics, has 6+ years of math education telling them that the y-axis is backwards.

I actually wrote an AngularJS directive to assist in integrating D3.js with automatic scope updates: https://github.com/beefsack/angular-d3

A little demo is in the repo too: http://rawgithub.com/beefsack/angular-d3/master/example/inde...

Excellent tutorial. It really reminds me of when d3.js clicked for me and I had the very same mental process you're describing in this post.

I'm glad you liked it, I believe d3.js can feel foreign since the separation between accessors and objects is really not obvious.

Everything looks functional until you dig in the source and realize that you are actually manipulating objects.

After spending the summer working on a project using Firebase, Angular, and D3, I definitely would have appreciated more articles on using D3 with dynamic data. Thanks for writing this up! I hope it helps some more people down the road.

Why are there only 3 points in each graph when there are five items in JSONdata? I can't figure it out.

Also:

When you show the JSONdata object on the page, you've switched your </code> and </pre> closing tags.

and

By reading through the code examples, it seems like you don't add the circles' click handler and cursor style until the Outside the current (domain) section, when it's really been there since the first example. That's a little confusing.

> Why are there only 3 points in each graph when there are five items in JSONdata? I can't figure it out.

Well this was a sneaky bug: There's an extra space at the end of the date in JSONData's last 2 elements(in the example and in the real code). This is why the last two were generating garbage value.

Wordpress is a real pain to work with when using code and it seems I introduced a bug when copying code over. It's going to be fixed shortly. As for the </code></pre>. Typo, my bad.

Regarding the CSS, I believe all the graphs behave the same way. Could you verify? I also can be reached @pothibo on twitter for further discussion ;)

I really appreciate your feedback.

(Edit: Gave the reason why the graph was only representing 3 data point instead of 5)

>Well this was a sneaky bug: There's an extra space at the end of the date in JSONData's last 2 elements(in the example and in the real code). This is why the last two were generating garbage value.

Thanks for that - my d3 understanding is tenuous, and I thought that it might have been even worse than I thought:)

>Regarding the CSS, I believe all the graphs behave the same way. Could you verify?

Not actually the css, but

  circles.enter()
   .append("svg:circle")
   .attr("style", "cursor: pointer;")
   .on("click", function(d) {d3.select("#demoAddRandom .value").text("Date: " + d.created_at + " amount: " + d.amount)

All the graphs do behave the same way, but that code isn't introduced in the examples until the first time you refactor refreshGraph. It's always there in the actual code of the graphs.

Oh wow, that was never suppose to be a part of the code I was showing. My apologies.

Wordpress is a real mess when dealing with code & text. Everything is part of the same big textarea and because there's no code highlighting, I have to read everything again and again and again.

Should be fixed now. Thanks!

I think that it's worth it to keep in the code examples - because it's simple code to understand, and if you omit it newbies will be wondering if it's something that d3 is doing automatically.

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