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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 casesensitive) followed by
commaseparated 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 arrayvalued 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.

KCorrections

Functions for calculating Kcorrections.

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 Observatoryspecific 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.
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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:
topcatuser@jiscmail.ac.uk