Next Previous Up Contents
Next: Technical Note
Up: Algebraic Expression Syntax
Previous: Operators

### 7.8 Functions

Many functions are available for use within your expressions, covering standard mathematical and trigonometric functions, arithmetic utility functions, type conversions, and some more specialised astronomical ones. You can use them in just the way you'd expect, by using the function name (unlike column names, this is case-sensitive) followed by comma-separated arguments in brackets, so

        max(IMAG,JMAG)

will give you the larger of the values in the columns IMAG and JMAG, and so on.

The functions are grouped into the following classes:

Arithmetic
  Standard arithmetic functions including things like rounding, sign manipulation, and maximum/minimum functions.
Arrays
  Functions which operate on array-valued cells.
Bits
  Bit manipulation functions.
Conversions
  Functions for converting between strings and numeric values.
CoordsDegrees
  Functions for angle transformations and manipulations, with angles generally in degrees.
CoordsRadians
  Functions for angle transformations and manipulations, based on radians rather than degrees.
Coverage
  Functions related to coverage and footprints.
Distances
  Functions for converting between different measures of cosmological distance.
Fluxes
  Functions for conversion between flux and magnitude values.
Formats
  Functions for formatting numeric values.
Gaia
  Functions related to astrometry suitable for use with data from the Gaia astrometry mission.
Json
  Functions for working with JSON strings.
KCorrections
  Functions for calculating K-corrections.
Lists
  Functions which operate on lists of values.
Maths
  Standard mathematical and trigonometric functions.
Randoms
  Functions concerned with random number generation.
Shapes
  Functions useful for working with shapes in the (X, Y) plane.
Sky
  Functions useful for working with shapes on a sphere.
Strings
  String manipulation and query functions.
Tilings
  Pixel tiling functions for the celestial sphere.
Times
  Functions for conversion of time values between various forms.
TrigDegrees
  Standard trigonometric functions with angles in degrees.
URLs
  Functions that construct URLs for external services.
VO
  Virtual Observatory-specific functions.

Full documentation of the functions in these classes is given in Appendix B.1, and is also available within TOPCAT from the Available Functions Window.

- 7.8.1 Technical Note

Next Previous Up Contents
Next: Technical Note
Up: Algebraic Expression Syntax
Previous: Operators

TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk