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IDL REFERENCE MANUAL
CONTENTS

IDL Reference Manual

B. A. Sheil
Eliot R. Smith

31 JANUARY 75

This document describes a computer system for social science data analysis under development at Harvard University. Comments are cordially invited and may be addressed to the authors at

Computation Facility
Center for the Behavioral Sciences
William James Hall 1368
Harvard University
Cambridge, Mass. 02138

Copyright reserved by the authors.



CONTENTS

0. Introduction

1. The philosophy of IDL
2. The relation between IDL and PPL
3. The rest of this manual

1. Data representation

1. Array structure
2. Terminology
3. Missing data
4. Large arrays
5. Function generalization
6. Conversion between different representations

2. Basic system functions

1. Selection
2. Assignment
3. Function generalization control

1. Single argument functions
2. Multiple argument functions
3. User functions

4. Print and label control
5. Disc resident arrays

3. Arithmetic functions

1. ABS
2. Constants
3. Distribution functions
4. MAX
5. MIN
6. MOD
7. TRANSLATE

4. Array functions

1. ALLOC
2. DEAL
3. ELEMENTTYPE
4. FIND
5. FORM
6. REFORM
7. GENVEC
8. INVERT
9. JOIN
10. MATRIX.PROD
11. MODE
12. RANK
13. RECODE
14. REDUCE
15. SHAPE
16. RESHAPE
17. SORT
18. TRANSPOSE

5. Compression functions

1. COUNT
2. CROSS
3. MOMENTS
4. PAIRN
5. PARTITION

6. Analysis functions

1. ANOVA
2. EMS
3. HIST
4. NORM
5. PLOT
6. SWEEP

7. Data entry: the DATAFILE program

8. Data analysis with IDL

1. Ante data

1. Experimental design
2. Artificial data generation

2. Data

1. Data entry
2. Recoding, weighting, subsetting

3. Table statistics

4. Correlational statistics

1. Covariance and correlation
2. Unstandardised regression
3. Standardised regression
4. Regression residuals
5. Partial correlation

5. Group difference analyses

1. Non-parametric
2. Parametric (ANOVA)

APPENDICES

A. Basic concepts of computing, HRSTS, and PPL

B. List of operators and their associated functions

C. List of global variables and their initial values

D. List of functions and their formal definitions

E. Technical details

F. Sample protocols

References

Index

Glossary