Practical IDL Programming

by Gumley

• ISBN13: 9781558607002
• ISBN10: 1558607005
• Format: Paperback
• Copyright: 7/18/2001
• Publisher: Elsevier Science

Summary

Increasingly, scientists and engineers must quickly and efficiently analyze and visualize extremely large sets of data. Interactive Data Language, IDL, was designed to address just this need. A popular data analysis and visualization programming environment, IDL is used worldwide by scientists and engineers in fields as diverse as the physical sciences, medical physics, and engineering test and analysis. In Practical IDL Programming, Liam E. Gumley provides a solid foundation in the fundamentals of procedural programming in IDL. He presents concise information on how to develop IDL programmers that are well structured, reliable, and efficient. The example programs in the book demonstrate key concepts and provide functionality that can be applied immediately. In addition, the book offers readers practical tips and advice on IDL programming, which they would otherwise discover only after years of experience. While only modest prior programming experience is assumed, readers with experience in any procedural language will quickly translate their skills to IDL, learning the best programming practices for this new environment. Scientists, engineers, and students in educational, government, and commercial research and development environments will all appreciate the author's guidance in helping them effectively analyze and visualize data. * Presents a comprehensive and detailed treatment of IDL data types, operators, expressions, array operations, input and output, direct graphics, plotting and imaging, publication quality output, and graphical user interfaces. * Designed for novices and experienced IDL users and programmers alike. * Provides an accompanying Web site with downloadable versions of all IDL programs in the book and a link to downloadable demonstration versions of the IDL software.

Table of Contents

Foreword	v
David Stern
Acknowledgments	ix
Introduction	1	(14)
About This Book	2	(3)
Who Should Read This Book?	2	(1)
Why Write This Book?	3	(1)
What about Objects?	3	(1)
Supporting Materials	4	(1)
Typographic Conventions	4	(1)
Special Characters	5	(1)
About IDL	5	(2)
IDL in Perspective	6	(1)
Obtaining IDL	7	(1)
Obtaining IDL	7	(1)
Running IDL	7	(2)
Online Help	9	(2)
Outline of the Chapters	11	(4)
Fundamentals of IDL Syntax	15	(74)
Interactive and Compiled Modes	15	(2)
Interactive Mode	16	(1)
Compiled Mode	16	(1)
Variables	17	(7)
Data Types	18	(1)
Keeping Track of Variable Types	19	(1)
Type Conversions	19	(2)
Converting Floats to Integers	21	(1)
Converting Between String and Numeric Types	22	(1)
Variable Names	22	(2)
Introduction to Arrays	24	(5)
Creating Arrays	25	(1)
Array Storage Format	26	(1)
Functions for Creating Arrays	26	(2)
Floating-Point Grid Arrays	28	(1)
Array Indexing	29	(5)
Array Indexing Examples	30	(1)
Multidimensional Array Indexing Examples	31	(1)
One-Dimensional Indexing	32	(1)
Index Sampling	32	(1)
Multidimensional Index Sampling	33	(1)
Expressions and Arithmetic Operators	34	(10)
Type Conversion in Expressions	35	(1)
Guarding against Division by an Integer	36	(1)
Operators	36	(1)
Operator Precedence	37	(1)
Arithmetic Operations on Arrays	38	(2)
Operator Precedence and Efficiency of Array Operations	40	(1)
Minimum, Maximum, and Modulo Operators	41	(1)
Array and Matrix Multiplication Operators	42	(2)
Relational and Boolean Operators	44	(8)
Relational Operators	44	(2)
Boolean Operators	46	(1)
NOT Operator	47	(1)
AND Operator	48	(1)
OR Operator	48	(1)
xor Operator	49	(1)
Combining Relational and Boolean Operators	49	(1)
Ternary Operator	50	(1)
Bit Manipulation	51	(1)
Structures	52	(6)
Anonymous Structures	53	(2)
Arrays of Structures	55	(1)
Named Structures	56	(1)
Working with Structures	57	(1)
Pointers	58	(9)
Types of Pointers	59	(1)
Creating Pointers	60	(2)
Freeing Pointers	62	(1)
Checking Pointer Validity	62	(1)
Pointer Dereferencing	63	(2)
Avoiding Pointer Problems	65	(2)
Array Properties	67	(5)
Number of Array Elements	68	(1)
Array Size and Type	68	(2)
Minimum and Maximum Values	70	(1)
Mean, Variance, and Standard Deviation	71	(1)
Totals	71	(1)
Locating Values within an Array	72	(3)
Finding Values That Meet Selection Criteria	72	(2)
Working with One-Dimensional Indices from where	74	(1)
Finding Values That Don't Meet Selection Criteria	74	(1)
Array Recordering	75	(6)
Changing Array Dimensions	75	(2)
Reversing Array Elements	77	(1)
Rotating Arrays	77	(1)
Transposing Arrays	78	(1)
Shifting Arrays	79	(1)
Sorting Arrays	80	(1)
Finding Unique Array Values	80	(1)
Array Resizing	81	(8)
Resizing by an Integer Factor	81	(3)
Resizing to Arbitrary Size	84	(2)
Resizing to Arbitrary Size with Customized Interpolation	86	(1)
Removing Rows or Columns	87	(2)
Writing IDL Programs	89	(50)
Defining and Compiling Programs	89	(8)
Procedures	90	(1)
Functions	91	(1)
Naming and Editing Source Files	91	(1)
Manual Compilation	92	(1)
Automatic Compilation	93	(2)
Returning to the Main Level after an Error	95	(2)
Control Statements	97	(13)
if Statement	97	(2)
case Statement	99	(2)
for Statement	101	(1)
while Statement	102	(1)
repeat Statement	103	(1)
return Statement	104	(2)
goto Statement	106	(1)
switch Statement	106	(2)
break Statement	108	(1)
Continue Statement	109	(1)
Parameters and Keywords	110	(8)
Parameters	110	(1)
Keywords	111	(1)
Using Parameters and Keywords	111	(2)
Argument-Passing Mechanism	113	(2)
Extra Keywords	115	(1)
Extra Keyword Precedence	116	(1)
Extra Keyword Passing Mechanism	117	(1)
Checking Parameters and Keywords	118	(4)
Checking Input Parameters and Keywords	118	(2)
Don't Modify Input Parameters	120	(1)
Checking Boolean Keywords	121	(1)
Checking Output Parameters and Keywords	122	(1)
Scripts, Include Files, and Journaling	122	(3)
Scripts	122	(1)
Include Files	123	(1)
Journaling	124	(1)
Global Variables	125	(5)
Read-Only System Variables	125	(1)
Writable System Variables	125	(2)
User-Defined System Variables	127	(2)
Common Blocks	129	(1)
Error Handling	130	(5)
Intercepting Errors	131	(2)
Math Errors	133	(1)
Restting the IDL Session	134	(1)
Efficient Programming	135	(4)
Conserving Memory	135	(2)
Using Efficient Methods	137	(2)
Input and Output	139	(54)
Standard Input and Output	140	(7)
Writing to Standard Output	140	(3)
Reading from Standard Input	143	(1)
Free-Format Input	144	(1)
Reading from a String	145	(1)
Writing to a String	145	(1)
Legal and Illegal read Arguments	146	(1)
Working with Files	147	(4)
Opening Files	148	(1)
Selecting a File	149	(1)
Obtaining Information about Files	150	(1)
Closing Files	151	(1)
Reading and Writing Formatted (ASCII) Files	151	(6)
Reading a Formatted File	152	(3)
Writing a Formatted File	155	(2)
Reading and Writing Unformatted (Binary) Files	157	(14)
Reading an Unformatted File (Single Data Type)	157	(2)
Reading an Unformatted File (Mixed Data Types)	159	(1)
Reading a Fortran-77 Unformatted File	160	(1)
Repositioning the File Pointer	161	(1)
Byte Swapping (or Big-Endian versus Little-Endian)	162	(3)
Writing Binary Data to an Unformatted File	165	(1)
Programs to Write and Read Portable Binary Data	166	(3)
Reading Binary Data via an Associated Variable	169	(1)
Saving and Restoring IDL Variables	170	(1)
Scientific and Specialized Data Formats	171	(1)
Reading and Writing netCDF Files	172	(10)
Reading a Variable from a netCDF file	174	(2)
Reading an Attribute from a netCDF file	176	(1)
Discovering the Contents of a netCDF file	177	(3)
Writing to a netCDF file	180	(1)
Standard Attributes	181	(1)
Coordinate Variables	182	(1)
Reading and Writing HDF Files	182	(11)
Reading a Variable from a HDF file	183	(2)
Using a Wrapper Procedure to Read a Variable	185	(1)
Reading an Attribute from a HDF file	186	(1)
Discovering the Contents of a HDF file	187	(3)
Writing to a HDF file	190	(2)
Coordinate Variables	192	(1)
Direct Graphics	193	(32)
Graphics Devices	193	(4)
Selecting a Graphics Device	195	(1)
Configuring the Graphics Device	195	(2)
Display Modes	197	(8)
8-Bit Display Mode	197	(1)
24-Bit Display Mode	197	(1)
Display Mode Comparison	198	(1)
Obtaining Display Mode Information	199	(1)
Selecting a Display Mode: Windows and MasOS Platforms	200	(1)
Selecting a Display Mode: UNIX Platforms	201	(3)
Selecting a Display Mode via a Startup File	204	(1)
Graphics Window	205	(5)
Creating a Windows	205	(1)
Working with Existing Windows	206	(1)
Invisible Graphics Windows (Pixmaps) and Animation	207	(3)
Scrolling Graphics Windows	210	(1)
Working with Colors	210	(8)
Color Models	211	(1)
Indexed Color	211	(2)
Working with the Color Table	213	(2)
Color Table Updates in 24-Bit mode	215	(1)
Decomposed Color	216	(2)
Display Mode Troubleshooting	218	(7)
Plotting Data	225	(76)
Plotting Overview	226	(9)
Line Plots	226	(2)
Overplotting	228	(1)
Scatter Plots	228	(2)
Polar Plots	230	(1)
Plot Coordinates	231	(1)
Coordinate Conversions	232	(1)
Plotting in Normal and Device Coordinates	233	(1)
System Variables	234	(1)
Plot Positioning	235	(6)
Specifying a Plot Position	235	(2)
Computing a Plot Position	237	(2)
Positioning Multiple Plots	239	(2)
Plot Customization	241	(7)
General Plot Properties	241	(1)
General Axis Properties	242	(1)
Configuring Axis Range and Style	243	(1)
Creating Axes	244	(2)
Logarithmic Axes	246	(1)
Tick Marks and Labels	247	(1)
Plot Colors	248	(4)
Indexed Colors	249	(1)
Decomposed Colors	250	(2)
Titles, Labels, and Symbols	252	(5)
Titles	252	(2)
Labels	254	(1)
Mathematical Symbols	255	(2)
Error Bar, Histogram, and Bar Plots	257	(6)
Error Bar Plots	257	(3)
Histogram Plots	260	(12)
Bar Plots	272
Contour Plots	263	(7)
Contour Plotting Overview	264	(3)
Contouring Irregularly Spaced Data	267	(2)
Filled Contours	269	(1)
Mesh and Shaded Surface Plots	270	(11)
Mesh Surface Plots	271	(3)
Irregularly Spaced Data	274	(2)
Shaded Surface Plots	276	(4)
Combined Mesh and Shaded Surface Plots	280	(1)
Mapping	281	(20)
Creating a Map Projection	281	(3)
Configuring a Map Projection	284	(4)
Selecting Map Limits	288	(2)
Continental Outlines	290	(2)
Map Grid Lines	292	(2)
Contour Plots on Map Projections	294	(3)
Displaying Regularly Gridded Images on Map Projections	297	(4)
Displaying Images	301	(40)
Image Fundamentals	302	(2)
PseudoColor Images	302	(1)
TrueColor Images	303	(1)
Image Display Routines	304	(4)
Displaying Unscaled Images: tv	304	(1)
Displaying Scaled Images: tvscl	305	(2)
Bottom-up versus Top-down display	307	(1)
Keywords for tv and tvscl	307	(1)
Customizing Image Scaling	308	(10)
Image Scaling via bytscl	308	(3)
Color Table Splitting	311	(1)
Displaying Multiple Images with Separate Color Tables	312	(2)
Histogram Clipping	314	(3)
Histogram Equalization	317	(1)
Sizing the Image to Fit the Display	318	(5)
Computing Image Size and Offset Automatically	320	(3)
Displaying TrueColor Images	323	(3)
Displaying TrueColor Images in 24-Bit Display Mode	323	(1)
Displaying TrueColor Images in 8-Bit Display Mode	323	(3)
Displaying Images on the PostScript and Printer Devices	326	(6)
Displaying PseudoColor Images on the PostScript Device	326	(3)
Displaying PseudoColor Images on the Printer Device	329	(1)
Displaying TrueColor Images on the PostScript Device	330	(1)
Displaying TrueColor Images on the Printer Device	331	(1)
An Image Display Procedure	332	(9)
Creating Graphical Output	341	(50)
Bitmap and Vector Output Files	341	(2)
Creating Bitmap Output Files	343	(12)
Reading from the Display: tvrd	343	(1)
Reading from an 8-Bit Display	344	(2)
Reading from a 24-Bit Display	346	(1)
A Wrapper Function for tvrd	347	(2)
Selecting a Bitmap Output Format	349	(1)
Saving an 8-Bit Image to a Bitmap Output File	350	(1)
Saving a 24-Bit Image to a Bitmap Output File	351	(1)
A Program for Saving the Screen to a Bitmap Output File	352	(3)
Creating PostScript Output	355	(23)
Introduction to the PostScript Device	356	(1)
Configuring the PostScript Device	357	(3)
Setting Size and Offset Manually	360	(2)
Setting Size and Offset Automatically	362	(6)
Color PostScript Output	368	(1)
Using the Color Table in PostScript Mode	369	(1)
Reversed Background and Drawing Colors	370	(1)
Fonts Overview	371	(1)
PostScript Device Fonts	372	(1)
TrueType Fonts	373	(1)
Positioning Graphics in the Drawable Area	374	(1)
Adding an EPS Preview	375	(3)
Creating Printer Output	378	(13)
Selecting a Printer	379	(1)
Configuring the Printer Device	380	(1)
Setting Size and Offset Manually	381	(3)
Setting Size and Offset Automatically	384	(5)
Color Printer Output	389	(1)
Fonts and Positioning	390	(1)
Graphical User Interfaces	391	(70)
Introduction to GUI Programming	391	(7)
GUI Components (Widgets)	393	(1)
GUI Programming versus Procedural Programming	394	(1)
GUI Design	395	(3)
Creating Widgets	398	(27)
Widget Attributes	401	(1)
widget_base function	402	(1)
widget_button function	402	(4)
widget_draw function	406	(2)
widget_droplist function	408	(1)
widget_label function	409	(2)
widget_list function	411	(1)
widget_slider function	412	(2)
widget_table function	414	(2)
widget_text function	416	(1)
Widget Layout	417	(5)
Naming Buttons	422	(2)
Compound Widgets	424	(1)
Working with Existing Widgets	425	(1)
Setting Widget Properties: widget_control	425	(1)
Getting Widget Information: widget_info	426	(1)
Events and Event Handling	426	(14)
Event Structures	427	(3)
Event Management	430	(1)
Event Handlers and Application State Information	431	(4)
Multiple Instances of an Application	435	(5)
A GUI Application	440	(21)
Design Implications	441	(1)
Startup Procedure	442	(5)
Event-Handler Procedures	447	(8)
Service Procedures	455	(3)
Compiling and Running imgui	458	(3)
Appendix A IDL on the Internet	461	(4)
A.1 Resources by the Author	461	(1)
A.2 RSI Information	461	(1)
A.3 Newsgroup	462	(1)
A.4 Libraries	462	(1)
A.5 Searchable Library Database	462	(1)
A.6 Editors	463	(1)
A.7 PostScript Viewers	463	(1)
A.8 People	463	(2)
Appendix B Mathematical Routines	465	(10)
Appendix C Widget Event Structures	475	(8)
Appendix D Widget Properties	483	(4)
Appendix E Graphics Device Properties	487	(2)
Index	489