### GPOINTS

Plot points or lines between the data

#### Description:

General plotting application. This application can be used simply to plot a symbol at the position of each point, to plot a symbol whose size depends upon the values in the ZCOL data area, or to draw lines connecting the data points.

#### Usage:

gpoints action [symbol]

#### Parameters:

The type of plot to produce. This can be "C", "P" or "S", with the following meanings:
• "C" (connect) – This action simply draws straight line segments between the data points.

• "P" (points) – Draw a symbol at each of the data points. The symbol type that is used to mark each point is determined in one of 3 ways:

• If no SYMBOL parameter is supplied on the command line, and no symbol numbers have been read into the symbol data area by READF, the point style will be set by the current value of SYMBOL.

• If no SYMBOL parameter is supplied on the command line, and values have been read into the symbol data area by READF, the symbol number for each point will determine the style of the point plotted.

• If SYMBOL is specified on the command line, it will override each of the above options. The same specified symbol will be used to mark all points.

The value of the symbol index should be an integer which refers to the standard PGPLOT symbols.

• "S" (sizeplot) – This action uses the values stored in the ZCOL data area to determine the size of the plotted symbol. The value of each entry in the ZCOL data area is effectively used as an argument to a CHANGE CHEIGHT command before each point is plotted. The SCALE parameter can be used to make these values cover a reasonable range by multiplying the Z data values.

[The value is prompted for.]

##### SYMBOL = _INTEGER (Read and Write)
The PGPLOT symbol number that is used to mark the data points.

If a value is specified on the command line, it will be used for plotting symbols for all the data. If not value is specified on the command line, the application attempts to use the SYMCOL data for its symbols. If no symbol values have been read into the SYMCOL data area, the current value is used for all the data. The current value is initially set to 1.

##### SCALE = _REAL (Read and Write)
The scale factor used to multiply the ZCOL data values to get a reasonable range of symbol sizes when ACTION="S".

If no value is specified on the command line, the current value is used. The current value is initially set to 1.0.

Specifies the geometry that is to be used to plot the data. This is explained in more detail in the section on projections. Allowed values: "NONE", "TAN", "SIN", "ARC", "GLS", "AITOFF", "MERCATOR" and "STG".
This parameter is not specified on the command line. The value of the global parameter PONGO_PROJECTN is used. If PONGO_PROJECTN is not defined, the default value "NONE" is used.
The centre of the projection in RA (i.e. the angle must be specified as hh:mm:ss.sss). This parameter is only required for PROJECTION values other than "NONE".
This parameter is not specified on the command line. The value of the global parameter PONGO_RACENTRE is used. If PONGO_RACENTRE is not defined, the default value "0" is used.
The centre of the projection in declination (i.e. the angle must be specified as dd:mm:ss.sss). This parameter is only required for PROJECTION values other than "NONE".
This parameter is not specified on the command line. The value of the global parameter PONGO_DECCENTRE is used. If PONGO_DECCENTRE is not defined, the default value "0" is used.