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  • Documentation
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  • 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. Handlng 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

3. Variables & Expressions

  • 3.1 VARIABLES
    • Variable syntax
    • File variables
    • Pseudo-variables
      • Grids and axes of pseudo-variables
    • User-defined variables
    • Abstract variables
      • Missing value flags
      • Missing values in input files
      • Missing values in user-defined variables
      • Missingvalues in output NetCDF files
      • Displaying the missing value flag
    • Returning properties of variables
    • Variable and dataset attributes
      • SHOW ATTRIBUTE commands
      • Attribute keywords
      • Programmatic access to attributes
      • Editing attributes
      • Output attributes to NetCDF fies
      • Output Variables to NetCDF files
      • Packed data in NetCDF files
  • 3.2 EXPRESSIONS
    • Operators
    • Multi-dimensional expressions
    • Functions
      • MAX
      • MIN
      • INT
      • ABS
      • EXP
      • LN
      • LOG
      • SIN
      • COS
      • TAN
      • ASIN
      • ACOS
      • ATAN
      • ATAN2
      • MOD
      • DAYS1900
      • MISSING
      • IGNORE0
      • RANDU, RANDU2
      • RANDN, RANDN2
      • RHO_UN
      • THETA_FO
      • RESHAPE
      • ZAXREPLACE
      • XSEQUENCE, YSEQUENCE, ZSEQUENCE, TSEQUENCE
      • FFTA
      • FFTP
      • SAMPLEI
      • SAMPLEJ
      • SAMPLEK
      • SAMPLEL
      • SAMPLEIJ
      • SAMPLET_DATE
      • SAMPLEXY
      • SAMPLEXY_CLOSEST
      • SAMPLEXY_CURV
      • SCAT2GRIDGAUSS_XY
      • SCAT2GRIDGAUSS_XZ
      • SCAT2GRIDGAUSS_YZ
      • SCAT2GRIDLAPLACE_XY
      • SCAT2GRIDLAPLACE_XZ
      • SCAT2GRIDLAPLACE_YZ
      • SORTI
      • SORTJ
      • SORTK
      • SORTL
      • TAUTO_COR
      • XAUTO_COR
      • TAX_DAY
      • TAX_DAYFRAC
      • TAX_JDAY
      • TAX_MONTH
      • TAX_UNITS
      • TAX_YEAR
      • TAX_YEARFRAC
    • Transformations
      • General information about transformations
      • Transformations applied to irregular regions
      • General information about smoothing transformations
      • @DIN—definite integral
      • @IIN—indefinite integral
      • @AVE—average
      • VAR—weighted variance
      • MIN—minimum
      • @MAX—maximum
      • @SHF:n—shift
      • @SBX:n—boxcar smoother
      • @SBN:n—binomial smoother
      • @SHN:n—Hanning smoother
      • @SPZ:n—Parzen smoother
      • @SWL:n—Welch smoother
      • @DDC—centered derivative
      • @DDF—forward derivative
      • @DDB—backward derivative
      • @NGD—number of good points
      • @NBD—number of bad points
      • @SUM—unweighted sum
      • @RSUM—running unweighted sum
      • @FAV:n—averaging filler
      • @FLN:n—linear interpolation filler
      • @FNR—nearest neighbor filler
      • @LOC—location of
      • @WEQ—weighted equal; integration kernel
      • @ITP—interpolate
      • @CDA—closest distance above
      • @CDB—closest distance below
      • @CIA—closest index above
      • @CIB—closest index below
      • @MED-median smoother
      • @SMN--mininum smoother
      • @SMX--maximum smoother
    • IF-THEN logic ("masking")
    • Lists of constants ("constant arrays")
  • 3.3 EMBEDDED EXPRESSIONS
    • Special calculations using embedded expressions
  • 3.4 DEFINING NEW VARIABLES
    • Global, local, and default variable definitions
  • 3.5 DEBUGGING COMPLEX HIERARCHIES OF EXPRESSIONS