Tag Archives: ruby-processing

Interacting with Graphs : Mouse-over and lambda-queuer

In the previous post, I described how I’d put together a basic system to drive data selection/exploration through a queue. While generating more graphs, it became evident that the code for mouseover interaction followed a specific pattern. More importantly, using Basis to plot stuff, mandated that I look at the inverse problem; namely, determining the original point from the point under the mouse pointer. In this case, it was pretty simple, since I’m only dealing with 2D points. Here’s a video of how it looks like. The example shows the exploration of a covariance matrix.

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Driving data visualisation over a queue using RabbitMQ and lambda-queuer

One of the things which has bothered me ever since I took the dive into visualisation is the problem of interactivity. The aim of interacting with a visualisation is to drill down or explore areas of the visualisation which are (or seem) interesting. Put another way, we are essentially filtering the data from a visual standpoint. In most cases, mouse interactions may be sufficient. But what if I wanted to be able to filter the data programmatically and have the result reflected in the visualisation?

One way is to simply re-run the code which generates the visualisation each time we use a different filter. This is the simplest, and, in many cases, enough. In this case, the modification to the code is made in an offline fashion. What if we wanted to do the same, but while the program is running? This describes my attempt at one such implementation. Albeit still somewhat primitive, we’ll see where it ends up. For the purposes of demonstration, I used the Parallel Coordinates visualisation, which is available on GitHub. I’ll continue using Processing through Ruby-Processing for this description.
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A guide to using Basis (updated for v0.6.0+)

This is a quick tour of Basis. Find the source for Basis on GitHub. Installing Basis is pretty simple; just grab it as a gem for your JRuby installation. Brief notes on the installation can be found here.

UPDATE: Starting from version 0.6.0, Basis allows you to specify axis labels. Additionally, you can specify arrays of points instead of plotting points one at a time. When you do this, you can also specify a corresponding legend string, which will show up in a legend guide. See below for more details.

UPDATE: Starting from version 0.5.9, you can turn grid lines on or off. Additionally, the matrix operations implementation has been ported to use the Matrix class in Ruby’s stdlib.

UPDATE: Starting from version 0.5.8, you can customise axis labels, draw arbitrary shapes/text/plot custom graphics at any point in your coordinate system. See below for more details.

UPDATE: With version 0.5.7, experimental support has been added for drawing objects which aren’t points. Interactions with such objects is currently not supported. Additional support for drawing markers/highlighting in custom bases is now in.

UPDATE: Starting from version 0.5.1, Basis has been ported to Ruby 1.9.2, because of the kd-tree library dependency. Currently, there are no plans of maintaining Basis compatibility with Ruby 1.8.x. As an aside, I personally recommend using RVM to manage the mess of Ruby/JRuby installations that you’re likely to have on your machine.

UPDATE: Basis has hit version 0.5.0 with experimental support for mouseover interactivity. More work is incoming, but the demo code below is up-to-date, for now. The code below should be the same as demo.rb on GitHub.
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Basis: Plotting arbitrary coordinate systems in Ruby-Processing

One of the first things I realised while working on visualisations in Processing is that a lot of the work required in setting up coordinate systems and plotting them is somewhat of a chore. Specifically, for things like parallel coordinates, multiple axes, each with its own scaling, I initially ended up with some pretty ugly custom code for each case. I did look around in the Libraries section of the Processing website, but didn’t find anything specific to manipulating and plotting coordinate axes.
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Getting ActiveRecord to behave nicely with Ruby-Processing in JRuby

Really, all I wanted to do was use Processing from Ruby. jashkenas has kindly written a gem which does just that. There was only a slight wrinkle: I wanted to pull my data from MySQL through ActiveRecord. Well, JRuby makes this process slightly more interesting than usual, so I document the process here. To start off with, install the gem with:

sudo gem install ruby-processing

Go into the directory where the ruby-processing gem is installed, and from there into {ruby-processing.gem.dir}/lib/core. In my case, this was /usr/lib/ruby/gems/1.8/gems/ruby-processing-1.0.9/lib/core.
Once inside there, you’ll find a file named jruby-complete.jar. Get rid of it, because we’ll be replacing it with a fresh (and different) version of jruby-complete.jar. Download the 1.6.3 version of JRuby-complete jar file. Rename it to jruby-complete.jar and put it in place of the jarfile we just deleted.

One step remains: this jarfile does not contain the activerecord-jdbcmysql-adapter gem. Install that with:

java -jar jruby-complete.jar -S gem install  activerecord-jdbcmysql-adapter --user-install

You’re good to go now. One more thing, just remember to replace the ActiveRecord adapter string with “jdbcmysql” and allow usage of that gem in your code with:

require 'arjdbc'

.