Introduction to IDL Mark Piper, Ph.D. Barrett M Sather Exelis Visual Information Solutions Copyright © 2014 Exelis Visual Information Solutions. All Rights Reserved. IDL, ENVI and ENVI LiDAR are trademarks of Exelis, Inc. All other marks are property of their respective owners. The information contained in this document pertains to software products and services that are subject to the controls of the U.S. Export Administration Regulations (EAR). The recipient is responsible for ensuring compliance to all applicable U.S. Export Control laws and regulations. Version 2014-03-12 Contacting Us The Exelis VIS Educational Services Group offers a spectrum of standard courses for IDL and ENVI, ranging from courses designed for beginning users to those for experienced application developers. We can develop a course tailored to your needs with customized content, using your data. We teach classes monthly in our offices in Boulder, Colorado and Herndon, Virginia, as well as at various regional settings in the United States and around the world. We can come to you and teach a class at your work site. The Exelis VIS Professional Services Group offers consulting services. We have years of experience successfully providing custom solutions on time and within budget for a wide range of organizations with myriad needs and goals. If you would like more information about our services, or if you have difficulty using this manual or finding the course files, please contact us: Exelis Visual Information Solutions 4990 Pearl East Circle Boulder, CO 80301 USA +1-303-786-9900 +1-303-786-9909 (fax) www.exelisvis.com [email protected] Contents 1. About This Course . 1 Manual organization . 2 The course files . 3 Starting IDL . 4 2. A Tour of IDL . 7 Overview . 8 Scalars and arrays . 8 Reading data from files . 9 Line plots . 10 Surface plots . 11 Contour plots . 12 Displaying and processing images . 14 Exercises . 15 References . 16 3. IDL Basics . 17 IDL directory structure . 18 The IDL workbench . 19 Working directory . 24 Preferences . 24 4 Search path . 26 The IDL Help system . 27 References . 28 4. Line, Bar and Scatter Plots . .29 Graphics routines . 30 Reflectance spectra . 30 Boulder temperature data . 33 The sunspot cycle . 38 Exercises . 41 References . 42 5. Data Structures . .43 Variables . 44 Data types . 45 Arrays . 48 Lists and hashes . 53 Structures . 54 Strings . 56 Pointers . 58 Objects . 59 Exercises . 59 References . 60 6. Programming . .63 Programs . 64 Parameters . 69 Calling mechanism . 70 Operators . 72 Control statements . 75 Batch files . 82 Timing with TIC and TOC ..... 82 Programming tips . 83 Exercises . 83 References . 83 7. Images . .85 What is an image? . 86 HST imagery of the Carina Nebula . 86 Truecolor JPEG image . 90 Landsat 7 ETM+ image . 92 Exercises . ..