This application can be used to manage the values of attributes
associated with the current co-ordinate Frame of an NDF (title, axis
labels, axis units, etc.).
Each attribute has a name, a value, and a state. This application
accesses all attribute values as character strings, converting to
and from other data types as necessary. The attribute state is a
Boolean flag (i.e. TRUE or FALSE) indicating whether or not a value
has been assigned to the attribute. If no value has been assigned to
an attribute, then it adopts a default value until an explicit value
is assigned to it. An attribute value can be cleared, causing the
attribute to revert to its default value.
The operation performed by this application is controlled by
Parameter MODE, and can:
- display the value of an attribute;
- set a new value for an attribute;
- set new values for a list of attributes;
- clear an attribute value; and
- test the state of an attribute.
Note, the attributes of the PIXEL, GRID and AXIS Frames are managed
internally by the NDF library. They may be examined using this
application, but an error is reported if any attempt is made to
change them. The exception to this is that the
Domain attribute may
be changed, resulting in a copy of the Frame being added to the WCS
component of the NDF with the new Domain name. The AXIS Frame is
derived from the AXIS structures within the NDF, so the AXLABEL
and AXUNITS commands may be used to change the axis label or units
string for the AXIS Frame.