CFAuxiliaryLongLat: CF auxiliary longitude-latitude variable

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

CF auxiliary longitude-latitude variable

Description

This class represents the longitude and latitude variables that compose auxiliary coordinate variable axes for X-Y grids that are not longitude-latitude.

The class provides access to the data arrays for longitude and latitude from the netCDF resource, as well as all the details that have been associated with both axes. Additionally, this class can generate the index to extract values on a long-lat grid of the associated X-Y grid data variable using a user-selectable extent and resolution.

Auxiliary longitude-latitude grids are only supported for reading from a netCDF resource. Creating an instance of this class manually therefore has no practical purpose.

Active bindings

friendlyClassName

(read-only) A nice description of the class.

name

(read-only) The name of the auxiliary lon-lat grid.

grid_names

(read-only) Read the names of the longitude and latitude grid as a vector of length 2.

dimids

(read-only) Retrieve the dimension ids used by the longitude and latitude grids.

aoi

Set or retrieve the AOI for the long-lat grid.

lon

(read-only) Retrieve the longitude grid.

lat

(read-only) Retrieve the latitude grid.

lon_bounds

(read-only) Retrieve the boundary values of the longitude grid.

lat_bounds

(read-only) Retrieve the boundary values of the latitude grid.

extent

(read-only) Retrieve the extent of the longitude and latitude grids, including bounds if they have been set. The extent is reported as a numeric vector of the four elements minimum and maximum longitude and minimum and maximum latitude.

dim

(read-only) The dimensions of the longitude and latitude grids.

Methods

Public methods

• CFAuxiliaryLongLat$new()

• CFAuxiliaryLongLat$print()

• CFAuxiliaryLongLat$brief()

• CFAuxiliaryLongLat$sample_index()

• CFAuxiliaryLongLat$grid_index()

• CFAuxiliaryLongLat$clear_cache()

• CFAuxiliaryLongLat$detach()

• CFAuxiliaryLongLat$clone()

---

Method new()

Creating a new instance. It should normally not be useful to create an instance of this class other than upon reading a netCDF resource.

Usage

CFAuxiliaryLongLat$new(varLong, varLat, boundsLong = NULL, boundsLat = NULL)

Arguments

varLong, varLat

The CFVariable instances with the longitude and latitude grid values, respectively.

boundsLong, boundsLat

The CFBounds instances of the grid cells for the longitude and latitude, respectively, if set. Defaults to NULL.

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Method print()

Summary of the auxiliary longitude-latitude variable printed to the console.

Usage

CFAuxiliaryLongLat$print()

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Method brief()

Some details of the auxiliary longitude-latitude grid.

Usage

CFAuxiliaryLongLat$brief()

Returns

A 2-row data.frame with some details of the grid components.

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Method sample_index()

Return the indexes into the X (longitude) and Y (latitude) axes of the original data grid of the points closest to the supplied longitudes and latitudes, up to a maximum distance.

Usage

CFAuxiliaryLongLat$sample_index(x, y, maxDist = NULL)

Arguments

x, y

Vectors of longitude and latitude values in decimal degrees, respectively.

maxDist

Numeric value in decimal degrees of the maximum distance between the sampling point and the closest grid cell. If omitted (default), the distance is calculated from the nominal resolution of the grids.

Returns

A matrix with two columns X and Y and as many rows as arguments x and y. The X and Y columns give the index into the grid of the sampling points, or c(NA, NA) is no grid point is located within the maxDist distance from the sampling point.

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Method grid_index()

Compute the indices for the AOI into the data grid.

Usage

CFAuxiliaryLongLat$grid_index()

Returns

An integer matrix with the dimensions of the AOI, where each grid cell gives the linear index value into the longitude and latitude grids.

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Method clear_cache()

Clears the cache of pre-computed grid index values if an AOI has been set.

Usage

CFAuxiliaryLongLat$clear_cache()

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Method detach()

Detach the latitude and longitude from an underlying netCDF resource.

Usage

CFAuxiliaryLongLat$detach()

Returns

Self, invisibly.

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Method clone()

The objects of this class are cloneable with this method.

Usage

CFAuxiliaryLongLat$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

ncdfCF documentation built on Sept. 13, 2025, 5:07 p.m.