D3 interactivity Linegraph basic example

INTERACTIVITYIt’s alive!!!

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Why?Our data is large and multi-faceted---multiple parameters, data types, sources of information, etc.

At times it is difficult to explore it fully and build an integrated understanding of the system

Even with statistical or numerical analyses it is difficult to translate results to actual physical phenomena or situations in the data

It is important to be able to check our assumptions with active exploration of the system

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Module 23

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Compare:

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How?HTML, CSS, Javascript

HTML - HyperText Markup LanguageA webpage, if you will. This is just to hold the meat really.Don’t worry, this isn’t 1999 on MySpace.

CSS - Cascading Style SheetsThis is for styling our page elements in a sane and modular fashion

Javascript - ...just JavascriptThis is a programming language, no relation to Java (Thank God)

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But...How does it work?HTML is, for our purposes, more like just a dumb container.CSS is just to do styling on elements and isn’t needed to start.

REAL TALK: Javascript on its own...isn’t great.

BUT: There are tons of libraries for javascript that make it great to work with. The rate of libraries is also growing at an astonishing rate (for actual programming use check out node.js)

Specifically we will make heavy use of:jQuery (adds lots of methods, functional programming elements)d3.js (this is how we graph)

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What can d3 do?

http://mbostock.github.com/d3/ex/force.htmlhttp://square.github.com/crossfilter/http://bl.ocks.org/1136236

Pros: Easy to use, Web standard (with WebKit), SVG, Interactive

Cons: Examples are the primary reference material. There is an excellent primer by Scott Murray (http://alignedleft.com), but you have to get your hands dirty

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Case Study

Let’s graph a freaking time series!

What do we even input as data to this?JSONs (JavaScript Object Notation), Don’t worry it’s awesome.CSVs (Comma Separated Values)

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Our DataIt’s basically just a saved dictionary into a file.Python has a ‘JSON’ module that can import/export dictionaries as a json string for saving

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How do I do that?

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But how do I get it going?

Just tell it that it’s HTML

These are library imports

Importing supported styling

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Now....What?

Make a div

Call our script

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Getting our hands dirtyLoad our data, the graph creation is wrapped inside this (`$` is jQuery)

We populate thearrays with our

x and y data

Define the height and width for our graphic to be used later (this is important)

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Making a place to placeCreate our svg

to place our graphin (uses our width and height from

before)

We have to place our svg in a div (our

div had an id ‘party-viz’)

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Let’s place some data

We append a path, with our data, using a previously defined

line function

This is our function,it just iterates

through the data, returning the x and

y transformed positions for a point

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But now we need to know what’s a point

We add the data circles as a svg container type

Now we actually append and give the attributes for the

circles

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But wait, now let’s make this interactive

We use tipsy/jQuery to generate an

interactive tooltip

Return an appropriately

formatted string to display

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Now for looking at it!We can just open the .html file in a web browser or...

We need a server.WAIT ISN’T THAT HARD??????

We can use a super quick, simple server with python.In the directory with the page and code just do:

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Now, the moment of glory

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As helpI have a web template repo on bitbucket that you can use, with a special branch for this example.

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As a note

This is all really new, cool stuff.

As such, it requires effort on your part to make it work and understand it.

Not everything needs to be interactive/web. It takes work to do this, so think first if it is worth your time.

I am more than willing to help you, but there is one master of d3.js right now---the guy who wrote it.

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