NetCDF variable

This class represents a netCDF variable, the object that holds the properties and data of elements like dimensions and variables of a netCDF file.

Direct access to netCDF variables is usually not necessary. NetCDF variables are linked from CF data variables and axes and all relevant properties are thus made accessible.

Super class

ncdfCF::NCObject -> NCVariable

Active bindings

group

(read-only) NetCDF group where this variable is located.

handle

(read-only) Get the handle to the netCDF resource for the variable.

vtype

(read-only) The netCDF data type of this variable. This could be the packed type. Don't check this field but use the appropriate method in the class of the object whose data type you are looking for.

ndims

(read-only) Number of dimensions that this variable uses.

dimids

(read-only) Vector of dimension identifiers that this NCVariable uses.

netcdf4

(read-only) Additional properties for a netcdf4 resource.

CF

Register CF objects that use this netCDF variable, or retrieve the list of registered CF objects.

fullname

(read-only) Name of this netCDF variable including the group path from the root group.

is_packed

(read-only) Flag that indicates if the data on file is packed.

Methods

Public methods

• NCVariable$new()

• NCVariable$print()

• NCVariable$shard()

• NCVariable$detach()

• NCVariable$get_data()

• NCVariable$write_data()

• NCVariable$set_name()

• NCVariable$dimension()

• NCVariable$dim()

• NCVariable$clone()

Inherited methods

• ncdfCF::NCObject$attribute()
• ncdfCF::NCObject$print_attributes()
• ncdfCF::NCObject$write_attributes()

---

Method new()

Create a new netCDF variable. This class should not be instantiated directly, they are created automatically when opening a netCDF resource.

Usage

NCVariable$new(
  id,
  name,
  group,
  vtype,
  dimids,
  attributes = data.frame(),
  netcdf4 = list()
)

Arguments

id

Numeric identifier of the netCDF object.

name

Character string with the name of the netCDF object.

group

The NCGroup this variable is located in.

vtype

The netCDF data type of the variable.

dimids

The identifiers of the dimensions this variable uses.

attributes

Optional, data.frame with the attributes of the object.

netcdf4

Optional, netcdf4-specific arguments in the format of RNetCDF.

Returns

An instance of this class.

---

Method print()

Summary of the NC variable printed to the console.

Usage

NCVariable$print(...)

Arguments

...

Passed on to other methods.

---

Method shard()

Very concise information on the variable. The information returned by this function is very concise and most useful when combined with similar information from other variables.

Usage

NCVariable$shard()

Returns

Character string with very basic variable information.

---

Method detach()

Detach the passed object from this NC variable.

Usage

NCVariable$detach(obj)

Arguments

obj

The CFObject instance to detach from this NC variable.

Returns

obj, invisibly.

---

Method get_data()

Read (a chunk of) data from the netCDF file. Degenerate dimensions are maintained and data is always returned in its smallest type.

Usage

NCVariable$get_data(start = NA, count = NA)

Arguments

start

A vector of indices specifying the element where reading starts along each dimension of the data. When NA, all data are read from the start of the array.

count

An integer vector specifying the number of values to read along each dimension of the data. Any NA value in vector count indicates that the corresponding dimension should be read from the start index to the end of the dimension.

Returns

An array, matrix or vector with the requested data, or an error object.

---

Method write_data()

Write (a chunk of) data to the netCDF file.

Usage

NCVariable$write_data(d, start = NA, count = NA, ...)

Arguments

d

The data to write. This must have appropriate dimensions.

start

A vector of indices specifying the element where writing starts along each dimension of the data. When NA, all data are written from the start of the array.

count

An integer vector specifying the number of values to write along each dimension of the data. Any NA value in vector count indicates that the corresponding dimension should be written from the start index to the end of the dimension.

...

Other parameters passed on to RNetCDF::var.put.nc().

Returns

Self, invisibly.

---

Method set_name()

Change the name of the NC variable. The new name must be valid in the indicated group, it can not already exist in the group. The netCDF file must be open for writing to change the name.

Usage

NCVariable$set_name(new_name)

Arguments

new_name

The new name for the NC variable

Returns

Self, invisibly.

---

Method dimension()

Get the NCDimension object(s) that this variable uses.

Usage

NCVariable$dimension(id)

Arguments

id

The index of the dimension. If missing, all dimensions of this variable are returned.

Returns

A NCDimension object or a list thereof. If no NCDimensions were found, return NULL.

---

Method dim()

The lengths of the data dimensions of this object.

Usage

NCVariable$dim(dimension)

Arguments

dimension

Optional. The index of the dimension to retrieve the length for. If omitted, retrieve the lengths of all dimensions.

---

Method clone()

The objects of this class are cloneable with this method.

Usage

NCVariable$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.