Skip to main content
  • Home >
  • Documentation
  • FAQ
  • Downloads
  • Support
  • Current Release Notes
  • Ferret Users Guide
    • Users Guide Index
    • Commands Reference
    • 1. Introduction
    • 2. Data Set Basics
    • 3. Variables & Expressions
    • 4. Grids & Regions
    • 5. Animations & Gif Images
    • 6. Customizing Plots
    • 7. Handling String Data Symbols
    • 8. Working with Special Data Sets
    • 9. Computing Environment
    • 10. Converting to NetCDF
    • 11. Writing External Functions
    • Glossary
    • Appendix A: Functions
    • Appendix B: PPLUS Guide
    • Appendix C: Ferret-Specific PPLUS Enhancements
  • Previous Release Notes
  • Tutorials and Demos
    • Ferret Tour
    • DSG files: Discrete Sampling Geometries Demo
    • Ferret sorting demo
    • Fast Fourier Transforms demo
    • Empirical Orthogonal Functions demo
    • Ferret objective analysis demo
    • Ferret Palette Demo
    • Map projections
    • Ferret polygon vector demo
    • Ferret Graticules demo
    • Ferret Polytube Demo
    • Ferret Polymark Demo
    • Ferret Constant-Array demo
    • Ferret land_detail demo
    • COADS Tour
    • Levitus Tour
    • Use OPeNDAP
    • Ferret binary read demo
  • PyFerret
    • PyFerret Downloads and Install ../../faq/ferret-faqs.html
    • What is PyFerret?
    • Why use PyFerret?
    • PyFerret for the Ferret user
    • PyFerret command syntax: quick-start notes
    • PyFerret for the Python user
    • Graphics in PyFerret ?
    • New Ferret functionality
    • PyFerret Python functions and constants
    • PyFerret Python objects and methods
    • Ferret external functions in Python
    • Ferret Fortran external functions
    • PyFerret metadata-and-data dictionaries
  • OPeNDAP
    • OPeNDAP usage in Ferret
    • Use OPeNDAP Demo
    • Test OPeNDAP

7.4 AUTOMATICALLY GENERATED SYMBOLS

A number of useful symbols are automatically defined whenever Ferret sets up a plot. Following any plotting command issue the command SHOW SYMBOLS/ALL to see a list. These plot symbols are listed and described in Chapter 6. Additional symbols are also listed at the end of this chapter. For example, if we wish to place a label "hello" at the upper right corner of a plot we might do the following

yes? PLOT/I=1:100 SIN(I/6)
yes? LABEL/NOUSER ($ppl$xlen) ($ppl$ylen) 1 0 .2 hello

This labeling procedure would work regardless of the aspect ratio of the plot. Use the command SHOW SYMBOL/ALL to see the symbols (and see "General Global Symbols" in the PLOT+ Users Guide).

7.5 USE WITH EMBEDDED EXPRESSIONS

When used together with Ferret embedded expressions,symbols can be used to perform arithmetic on the plot geometry. For example, this command will locate the plot title in bold at the center of a plot regardless of the aspect ratio:

yes? LABEL/NOUSER `($ppl$xlen)/2` `($ppl$ylen)/2` 0 0 .2 @AC($labtit)