Visualizations may be very helpful in understanding data better. There is a whole range of visualizations, from rather simple scatter and barplots up to projections of high dimensional data or even entire genomes. Many of these visualizations often require a lot of tweaking and changes in settings like zooming in and assigning colors, etc. Therefore, visualizations are ideally interactive, and changing settings is often an initial step in exploring data. For this reason it may be inconvenient to make use of static galaxy tools because it lacks these interactive features. For these situations Galaxy offers the option to create visualizations plugins, file format specific javascripts that integrate with the history menu, without making redundant copies of data.
In this tutorial we shall go through how this system works and create a simple visualization plugin. The tool will create a visualization of the number of aligned reads per chromosome of a BAM file, and we will discuss possible optimizations and advantages and disadvantages of the proposed implementation.