# Coding a dynamic systems and controlling it via a graphical user interface

**gRaphics!**, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)

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My work, in the past year, has consisted mostly of coding dynamic models in R, models which I will soon be exporting to a server-based R implementation, possibly thanks to rApache.

I ususally run my models through an input file where I specify all parameters needed, but for the end users, we felt it may be better to provide a graphical user interface where they could select just a few parameters, with the others defaulting to meaningful values.

Wioth this post I want to quickly illustrate all that’s needed to put such a system together, exception made for the rApache part. I’ve not made any steps in that direction, yet.

So, let’s start by defining a dynamic model, which we’ll integrate using the *deSolve* package. We use the Lorentz system, which is far simpler than any of the models I actually work with, and produces much more beautiful and interesting graphics, too.

OK, if you run this you’ll obtain a variable called ‘out’, which contains the X/Y/Z coordinates of your system at different time instants in the phase space. You can look at the values directly, but obviously plotting is a good option. Taking advantage of the ‘multiplot’ function defined in the Cookbook for R, we can write:

Which will generate the following picture:

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