## Changes Introduced in V4.5

The following describes the most significant changes that occurred in the AST library between versions V4.4 and V4.5:

1. All FITS-CLASS headers are now created with a frequency axis. If the FrameSetFrameSet supplied to astWriteastWrite contains a velocity axis (or any other form of spectral axis) it will be converted to an equivalent frequency axis before being used to create the FITS-CLASS header.

2. The value stored in the FITS-CLASS keyword “VELO-LSR” has been changed from the velocity of the source to the velocity of the reference channel.

3. Addition of a new method call astPurgeWCSastPurgeWCS to the FitsChanFitsChan class. This method removes all WCS-related header cards from a FitsChan.

4. The PlotPlot class has a new attribute called GrfContext that can be used to comminicate context information between an application and any graphics functions registered with the Plot class via the astGrfSetastGrfSet function.
5. Functions registered with the Plot class using astGrfSet now take a new additional integer parameter, “grfcon”. The Plot class sets this parameter to the value of the Plot's GrfContext attribute before calling the graphics function. NOTE, THIS CHANGE WILL REQUIRE EXISTING CODE THAT USES astGrfSet TO BE MODIFIED TO INCLUDE THE NEW PARAMETER.
6. The astRebinSeq functions now have an extra parameter that is used to record the total number of input data values added into the output array. This is necessary to correct a flaw in the calculation of output variances based on the spread of input values. NOTE, THIS CHANGE WILL REQUIRE EXISTING CODE TO BE MODIFIED TO INCLUDE THE NEW PARAMETER (CALLED "NUSED").
7. Support has been added for the FITS-WCS “HPX” (HEALPix) projection.
8. A new flag “AST__VARWGT” can be supplied to astRebinSeq. This causes the input data values to be weighted using the reciprocals of the input variances (if supplied).

9. The FrameFrame class has a new read-only attribute called NormUnit that returns the normalised value of the Unit attribute for an axis. Here, “normalisation” means cancelling redundant units, etc. So for instance, a Unit value of “s*(m/s)” would result in a NormUnit value of “m”.

10. A new function astShowMeshastShowMesh has been added to the RegionRegion class. It displays a mesh of points covering the surface of a Region by writing out a table of axis values to standard output.

11. The Plot class now honours the value of the LabelUp attribute even if numerical labels are placed around the edge of the Plot. Previously LabelUp was only used if the labels were drawn within the interior of the plot. The LabelUp attribute controls whether numerical labels are drawn horizontally or parallel to the axis they describe.

12. A bug has been fixed that could segmentation violations when setting attribute values.