Contents

• Section 0: Some basic UNIX commands
• Section 1: A first program, a first plot and using IDL on the command line
  • A first program
  • Some simple sums
  • A very simple plot using three arrays
  
  
• Section 2: Introduction to IDL functions and procedures
  • An example function (of one variable)
  • Another example functions (of multiple variables)
  • Using keywords
  • A first IDL procedure: an example reading data from a file
  • Using where
  • Using where on a 2D array
  • Plotting two lots of 1D data on the same graph
  
  
• Exercise 1: Plotting some aircraft data
• Section 3: Some ``nuts and bolts'' of IDL (Hugh Pumphrey, University of Edinburgh)
  • Variables, data types
  • Arrays
  • Flow Control
  • Array operations
  
  
• Section 4: More reading and writing data, some 2D plots
  • A first two 2D line contour plot
  • A filled contour plot
  • Contouring onto a map and writing to .png
  • Contouring onto a map and writing to .ps
  • Colours in IDL
  • A first 2D colour contour plot
  • E.g. Finding files and then contouring the irregularly gridded data
  
  
• Exercise 2: Plotting Saharan Albedo and reading binary data
• Section 5: Images
• Section 6: Final thoughts
  • IDL-meteorology haiku
  
  
• Appendix: IDL setup
• Appendix II: Other tips and tricks
  • Contours on images
  • Colorbars
  • Plotting wind vectors
  • Plotting 3D surfaces
  • Loops and how to avoid them
  • Dimensional Juggling (from David Fanning)
  • Array concatenation (from David Fanning)
  • The Histogram routine
  • Other questions
  • NetCDF (from Justin Peter)
  • Adapting built-in IDL code

Abstract:

These webpages are intended to provide you with a brief introduction to the IDL (Interactive Data Language) scientific graphics package. They cover all that you need to know to get yourself started using IDL and to begin producing useful results. They certainly will not teach you everything that IDL can do - that would take a whole term or more. It is important to remember that learning any computing language or package is largely a matter of practice. You will not learn much by just listening to me. I can show you the sort of things that can be done and I can show you how to get started. Becoming proficient is up to you.

The people you work with during your PhD will probably have lots of code to do the kind of things that you want to do. You will probably use that and build on it. This course is just meant to get you started with the basics, rather than teach you the tricks for handling the data/creating the specific style of plots etc that you will need to do.

These notes do not assume any knowledge of IDL at all. They do assume that you are comfortable using UNIX. If you have programmed in C or Fortran before you find them rather simple at first. If you have not programmed before in any language, then starting can be confusing, but most people get the hang of it quite quickly.

I assume you can use UNIX to edit text files, create directories and move files around -- I have included a first page that summarises some basic UNIX commands in case you have not.