### POLSELECT

Select vectors from a catalogue

#### Description:

This application creates an output catalogue that contains a subset of the vectors in the specified input catalogue. The subset can be specified in various ways (see parameter MODE):
• using the bad pixels in a reference image to mask out unwanted vectors

• using ARD or AST region specifications to select the required vectors

• using an algebraic expression to select the required vectors on the basis of their column values

#### Usage:

polselect in out mode

#### Parameters:

This parameter is only used if parameter MODE is set to " EXPRESSION" . It should be set to a boolean expression that uses column names from the input catalogue as variables. It should have the format used by the CURSA ’ CATSELECT’ command (see sun/190). In general, the arithmetic and boolean operators available in either C and Fortran can be used (e.g. ’ .ge.’ , ’ $>$=’ , ’ .and.’ , ’ &&’ , etc.), as can the usual mathematical functions (e.g. ’ abs’ , ’ tan’ , ’ pow’ , etc). A vector is selected if the expression evaluates to TRUE (if using a Fortran-style expression) or a non-zero value (if using a C-style expression).
The name of the input catalogue. A file type of .FIT is assumed if none is provided.
If FALSE, all selected vectors are copied to the output catalogue. If TRUE, all unselected vectors are copied to the output catalogue. [FALSE]
This parameter is only used if parameter MODE is set to " MASK" . It specifies the two-dimensional NDF to be used as a mask to select the required vectors. Vectors corresponding to good pixel values in the mask are selected. The mask is assumed to be aligned with the catalogue in pixel coordinates.
• " MASK" : The image specified by parameter MASK is used to select the vectors. If a vector has a position that corresponds to a good pixel in MASK, then the vector is selected.
• " REGION" : The ARD or AST region specified by parameter REGION is used to select the vectors. If a vector falls within the region, then it is selected.
• " EXPRESSION" : The boolean expression specified by parameter EXP is used to select the vectors. If the boolean expression evaluates to TRUE for a vector, then the vector is selected.
This parameter is only used if parameter MODE is set to " REGION" . It specifies the NDF to which the ARD description refers. It is used to define the pixel coordinate system used by the ARD description. If null (!) is supplied, it is assumed that the pixel coordinate system used by the ARD description is the pixel coordinate system of the input catalogue. [!]
This parameter is only used if parameter MODE is set to " REGION" . It should be set to the name of a text file containing a description of the region containing the vectors to be selected. This can either be in the form of an ’ ARD description’ (see SUN/183), or an ’ AST Region’ (see SUN/210).