Heroku is a great platform, but it do has some limitations in its free service. One of those is the maximum on the number of rows in the PostgreSQL database and the total size limit. Recently I received an e-mail stating that my database exceeded that number of records. This post will show how to inspect your database to find the problem via the Heroku toolbelt and connect to your database with pgAdmin III.

The Model-View-Controller design pattern as used by Ruby on Rails is very clear. Each part has its own role to play. But sometimes there is a bit of a gap. For instance, when determining specific attribute values of elements in a View, it is often not clear where these calculations should take place. We could create a set of helper methods, but that would clutter the namespace. Furthermore, the helper methods are hard to group by their relation, in contrast with Classes and Modules. Instead, we use the Presenter Design Pattern for this type of problems. This post shows how to use this pattern in Ruby on Rails and how to interact with it from the View.

During the event of the World Port Days the Port of Rotterdam organized their first hackathon. The goal was to create an application using recently opened datasets from the port: data about the position of ships and geo-information about the port. Our team built the Maelstrom app, which visualizes the risk of congestion on the water.

In this open letter to the LinkedIn User Experience Team (or someone else who is willing to read this) I highlight a few irritations a have concerning the website.

Traditionally, many classification problems try to solve the two or multi-class situation. The goal of the machine learning application is to distinguish test data between a number of classes, using training data. But what if you only have data of one class and the goal is to test new data and found out whether it is alike or not like the training data? A method for this task, which gained much popularity the last two decades, is the One-Class Support Vector Machine. This (quite lengthly) blog post will give an introduction to this technique and will show the two main approaches.

In the previous post in this series we have looked at creating SVG graphs. We constructed the graph using parts as the visual grid, data points, surfaces and text labels. In this post we will look at the ability to interact with the graph and add some nice animations.

In a series of two posts we take a look at building interactive graphs with SVG, CSS and Javascript. We take a real-world example from one of our projects and show you our approach. The final goal is an interactive graph (think animations, shadows and tooltips) using a jQuery-SVG plugin.

A real programmer is lazy, right? Every now and then you find yourself doing a repetitive tasks consisting of a few small steps. The steps are fast to perform, but still… it just feels… wrong. It should be automated! Thanks to AppleScript this is an “easy” task. I will show my approach and problems I found.

Every major application or breakthrough starts with just a simple idea. But an idea that has developed in the mind of one needs to tested to the real world, and preferably in an easy and fast manner. During a research project on recognizing human activities using accelerometer data, the need for quick visualizations of collected data emerged. Using a simple setup this is made possible, for everybody with an Android smartphone.