Package index • ncdfCF

Main ncdfCF classes and operations

Opening and inspecting netCDF resources

NetCDF resources can be accessed on local (or networked) file systems, or on THREDDS server on the internet. NetCDF resources are opened by default for read-only access but local resources may be opened for writing as well (THREDDS servers do not support writing).

open_ncdf(): Open a netCDF resource
peek_ncdf(): Examine a netCDF resource

Data set

The main object that the ncdfCF package presents to the R user is a CFDataset. When opening an existing netCDF resource, the CFDataset will provide access to all data variables and associated objects in the resource, including its attributes, in a ready-made way for usage. The CF Conventions will have been applied and the objects within the CFDataset are thus fully formed and linked.

create_ncdf(): Create a new data set
as_CF(): Create a CFDataset or CFVariable instance from an R object
CFDataset: CF data set
CFGroup: Group for CF objects
names(<CFDataset>): Names or axis values of an CF object
groups(): List the groups in the CF object, recursively.
`[[`(<CFDataset>): Get a CF object from a data set

Data variable

A data set can hold one or more data variables. A data variable is the object that holds the data and descriptive metadata for a variable of interest, such as daily maximum temperature. In R you can operate directly on a data variable but it can also be subsetted, profiled and summarised over the “time” dimension. It can be saved to a new netCDF resource or exported to some other format.

CFVariable: CF data variable
CFVariableL3b: CF data variable for the NASA L3b format
CFGridMapping: CF grid mapping object
CFCellMeasure: CF cell measure variable
CFAuxiliaryLongLat: CF auxiliary longitude-latitude variable
`[`(<CFVariable>): Extract data for a variable
`[`(<CFVariableL3b>): Extract data for a variable
aoi(): Area of Interest
dim(<AOI>): The dimensions of the grid of an AOI
Ops(<CFVariable>) Math(<CFVariable>): Operations on CFVariable objects

Axes

The shape of a data variable is described by the set of axes that it links to. There are specialised axes for specific types of axes, such as for longitude and latitude, or more generic types, each having their own class inheriting from the “virtual” CFAxis class.

makeAxis(): Create an axis
makeCharacterAxis(): Create a character axis
makeDiscreteAxis(): Create a discrete axis
makeLongitudeAxis(): Create a longitude axis
makeLatitudeAxis(): Create a latitude axis
makeTimeAxis(): Create a time axis
makeVerticalAxis(): Create a vertical axis
CFAxis: CF axis object
CFAxisCharacter: CF character axis object
CFAxisDiscrete: CF discrete axis object
CFAxisNumeric: Numeric CF axis object
CFAxisLongitude: Longitude CF axis object
CFAxisLatitude: Latitude CF axis object
CFAxisTime: Time axis object
CFAxisVertical: Vertical CF axis object
CFVerticalParametricTerm: Parametric formula term for a vertical CF axis object
CFLabel: CF label object
dim(<CFAxis>): Axis length

ncdfCF objects

This package uses many base classes to “glue” all the objects together. In typical use of the package these classes are not very useful, the higher-level objects encapsulate these low-level objects. For developers it could be useful to study or directly access these classes.

CFObject: CF base object
CFBounds: CF boundary variable
CFData: CF data object
CFStandardNames: CF Standard names table

NetCDF objects

When opening an existing netCDF resource, or after writing a new netCDF file, the contents of the netCDF resource are captured in a hierarchy of NC objects. These objects are immutable for the R user because they reflect what is in the resource.

NCResource: NetCDF resource object
NCObject: NetCDF base object
NCGroup: NetCDF group
NCDimension: NetCDF dimension object
NCVariable: NetCDF variable