NEWS.md
In ncdfCF: Easy Access to NetCDF Files with CF Metadata Conventions

ncdfCF 0.5.0

Cell measure variables fully supported. External variables can be linked and are then automatically available to referring data variables.
Writing a CFArray instance to file automatically orients the data into the canonical axis order of X - Y - Z - T - others.
CFAxis has several methods added to work with multiple sets of auxiliary coordinates associated with the axis.
CFLabel has print() and write() methods.
CFVariable::subset() can subset over a discrete axis with auxiliary coordinates.
summarise() can now summarise over eras. This yields a climatological statistic which is now supported with the appropriate "time" axis description.
actual_range attribute is set on data arrays, axes and bounds.
Added CFDataset$var_names and CFDataset$axis_names fields.
Check for duplicate object names at group level added.
Axis values fields made private. Read-only access provided throughCFAxis$values and CFAxis$coordinates (preferred) for consistent access patterns throughout the axis class hierarchy.
Root group can print() without enclosing data set.
Fixed summarise() when temporal result yields scalar time axis.
Fixed writing bounds for a "time" axis.
Fixed saving a packed CFArray when the original netCDF file was packed as well.
Minor code fixes.
Documentation updates.

ncdfCF 0.4.0

CFData has been renamed CFArray to more accurately describe its contents.
CFArray objects can now be written to a netCDF file.
Methods CFVariable$summarise() and CFArray$summarise() summarise the temporal dimension of a data object to a lower resolution using a user-supplied function, using the specific calendar of the temporal dimension and returning a new CFArray object with the summarised data for every return value of a call to the function, i.e. the function may have multiple return values. The CFArray version is much faster (because all data has been read already), but the CFVariable version can also summarise data variables that are too big to fit into the available memory entirely. In either case, code is optimized compared to the R base version so an operation over the "time" dimension of a data array is about twice as fast as using the base R apply(X, MARGIN, tapply, INDEX, FUN, ...) call.
Method CFArray$data.table() exports a data object to a data.table.
CFVariable and CFArray classes now have time() method to retrieve the "time" axis or its CFTime instance, if present.
CFAxis has new coordinates field with which to retrieve the coordinates along the axis.
New attributes can be defined on any object that supports attributes, or deleted.
Fixed error on reading bounds for auxiliary coordinate variables. Various other minor code fixes.
CFResource fixed to conform to new R6 version.
Documentation updated, including vignettes.

ncdfCF 0.3.0

Function peek_ncdf() returns quick-view information on a netCDF resource.
String-valued labels for discrete and generic numeric axes are now supported, including multiple label sets per axis. The labels are associated with an axis rather than a data variable (as the CF documents imply) and the axis must be explicitly defined (as the CF documents imply but not explicitly state, and it is missing from the example given).
Functions makeMemoryGroup(), makeLongitudeAxis() and makeLatitudeAxis() added to create scaffolding for new CF objects.
NCGroup::unused() method identifies unused NCVariables to aid in finding issues with netCDF resources.
print() method for NCVariable and NCDimension.
Method CFObject$fullname added, giving fully-qualified CF object name.
"Axis" associated with bounds variable is no longer created.
NASA level-3 binned data (L3b) is now supported.
Reference to a containing NCGroup moved down to CFObject for CF objects.
Minor code fixes.
Documentation extended and formatting fixed, new vignette.

ncdfCF 0.2.1

NetCDF groups are now fully supported, including traversing group hierarchies with absolute or relative paths.
All axis types are identified correctly. This includes:
Regular coordinate axes (a.k.a. NUG coordinate variables).
Discrete axes, even when no coordinate variable is present - an extension to the CF conventions.
Parametric vertical axes, but values are not yet computed.
Scalar axes, linked to variables through the "coordinates" attribute of the latter.
Auxiliary longitude-latitude grids, the horizontal component of the grid of a variable that was not defined as a Cartesian product of latitude and longitude, using the "coordinates" attribute of the variable. When subsetting a data variable, resampling is automatically performed.
The four axes that "receive special treatment" by the Conventions each have a separate class to deal with their specific nature: CFAxisLongitude, CFAxisLatitude, CFAxisVertical, and CFAxisTime.
Bounds are read and interpreted on all axes except the vertical axis, including any auxiliary long-lat grids.
Information on UDTs is captured in a separate class. This is effectively only supported for the "compound" sub-type, for scalar values only.
Data is read into the most compact form possible. This saves a significant amount of memory when large integer variables are read as they would remain integers rather than the default numeric type.
Data is returned from CFVariable$subset() as an instance of the CFData class, with associated objects such as axes and the attributes from the variable. Data can be read out in a variety of forms, currently as a raw array, an oriented array or as a terra::SpatRaster or terra::SpatRasterDataset.
Full support for grid mapping variables. As a significant extension over CF Metadata requirements, CRS strings are produced in the OGC WKT2 format, using the latest EPSG database of geodetic objects.
Improvements in printing object details.
Code refactored to R6.
GHA enabled

ncdfCF 0.1.1

objects_by_standard_name() will list objects in the netCDF resource that have a "standard_name" attribute.

ncdfCF 0.1.0

Initial CRAN submission. This is a WORK IN PROGRESS and the package is not yet fit for a production environment.
This version supports reading from netCDF resources. CF Metadata Conventions are used to set properties on axis orientation, time dimensions and bounds.
Standard R commands can be used to inspect properties of the netCDF resource, such as dimnames() and length().
Access to data uses the R standard [ selection operator for use with dimension indices. Use real-world coordinates with subset().