ncdfCF-package {ncdfCF}R Documentation

ncdfCF: Easy Access to NetCDF Files and Interpreting with CF Metadata Conventions

Description

Support for accessing and interpreting netCDF datasets in a familiar R style. Built on top of the RNetCDF package, built and maintained by the developers of the netcdf library, package ncdfCF provides high-level access to netCDF resources. Resources are matched against the Climate and Forecast (CF) Metadata Conventions for climate and forecasting data, current version 1.12. The CF Metadata Conventions is widely used for distributing files with climate observations or projections, including the Coupled Model Intercomparison Project (CMIP) data used by climate change scientists and the Intergovernmental Panel on Climate Change (IPCC), as well as large collections of satellite imagery, including from Landsat and MODIS.

Details

This package currently supports group traversal with scoping rules, axis determination and interpretation, including auxiliary axes, time axis interpretation with all defined calendars, grid mapping, use of bounds data, manipulating and interpreting attributes of groups (including global attributes) and variables, search for and use of standard names. Some specific constructs in CF are also supported:

Properties of the netCDF resource objects are easily examined using common R commands. Access to the data in the variables can be had using similarly known patterns, and data can be exported to a variety of formats.

This package is intended to access data from netCDF resources in a format that is easily integrated with other R coding patterns and packages, with full support for the CF Metadata Conventions that define the data properties. This package does very little beyond that; specifically, there is no support for spatial analysis, mosaicing, changing the coordinate reference system (i.e. projection), or any significant form of data analysis at all. The user is directed to other packages for such functionality.

Global functions

Data set

A CFDataset is the object that contains a netCDF resource. This is the main class that you need to access netCDF data.

S3 methods for CFDataset

Data variable

A CFVariable contains a single data variable from a data set. It contains detailed information on the data variable and there are functions to access the data, with different selection methods.

Properties

Data extraction

S3 methods for CFVariable

Axis

The CFAxis class is the common ancestor of specialized classes that represent specific types of axes. These sub-classes are the ones that are actually returned when retrieving an axis. These classes are:

Any scalar axes that are found in a netCDF file are converted to one of the above axis classes, with a length of 1.

Any of the axis classes can have one or more coordinate sets associated with them. This is most useful for CFAxisDiscrete. Labels of the active coordinate set are used for display of axis properties, as well as for selection in e.g. CFVariable$subset().

Methods for CFAxis instances:

Properties

Extraction

Coordinates

S3 methods for CFAxis

Data

The CFVariable::data() and CFVariable::subset() methods return a CFArray object to the caller. The CFArray object contains the data from the netCDF resource, as well as important metadata from the data variable: axes, CRS and attributes. The data is easily accessed as a raw array, or processed to some other format.

Properties

Data extraction

Author(s)

Maintainer: Patrick Van Laake patrick@vanlaake.net [copyright holder]

See Also

Useful links:


[Package ncdfCF version 0.6.1 Index]