CATGRID - Generate an NDF grid from up to three columns in a catalogue

Description:

Generate a grid, formatted as a Starlink NDF file, from up to three columns in a catalogue. If one column is specified the output grid corresponds to a histogram, two columns correspond to a two-dimensional 'image' and three columns to a data cube.

The dimensionality of the grid (1, 2 or 3) is specified. Then, for each axis of the grid, the name of the corresponding column in the catalogue and the number of elements in the grid along the axis are given. The limits of the grid along each axis correspond to the range of values of the corresponding catalogue column. The value of each element in grid is set to the number of points which lie within it. Optionally the grid may be normalised by dividing by the total number of points in the catalogue.

The grids generated can be displayed and manipulated using Starlink software such as GAIA (SUN/214), KAPPA (SUN/95) and Figaro (SUN/86) or visualisation packages such as DX (SUN/203 and SC/2).

Usage:

catgrid

Parameters:

CATIN = CHARACTER (read)

Name of the input catalogue.

NDIM = INTEGER (read)

Number of dimensions in the output grid. The permitted values are 1 - 3.

COLX = CHARACTER (read)

Name of the column to be used for the X-axis of the grid.

XBINS = INTEGER (read)

Number of bins in the grid along the X-axis.

COLY = CHARACTER (read)

Name of the column to be used for the Y-axis of the grid.

YBINS = INTEGER (read)

Number of bins in the grid along the Y-axis.

COLZ = CHARACTER (read)

Name of the column to be used for the Z-axis of the grid.

ZBINS = INTEGER (read)

Number of bins in the grid along the Z-axis.

GRID = NDF (Write)

The name of the output data grid or histogram.

NORMAL = LOGICAL (read)

Flag indicating whether the grid of values is to be normalised or not. If NORMAL is set to TRUE the grid will be normalised (that is, the value of each grid element will be the number of points occupying the element divided by the total number of points in the catalogue); if it is set to FALSE it will not. The default is FALSE.

QUIET = LOGICAL (read)

Operate in quiet mode where warnings are suppressed. The permitted values are: TRUE - quiet mode, FALSE - verbose mode.

Examples:

catgrid

The input catalogue will be prompted for, followed by the dimensionality (1, 2 or 3) of the output grid. For each axis the name of the corresponding catalogue column and the number of elements along the axis are prompted for. Finally, the name of the NDF file to hold will be prompted for. An un-normalised grid will be generated.

catgrid normal=true

The input catalogue, dimensionality, details of each axis and output NDF file are all prompted for. A normalised grid will be generated.