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7.7 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.
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.


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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