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)

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.

• 7.7.1 Technical Note