CFAxisVertical: Vertical CF axis object

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

Vertical CF axis object

Description

This class represents a vertical axis, which may be parametric. A regular vertical axis behaves like any other numeric axis. A parametric vertical axis, on the other hand, is defined through an index value that is contained in the axis coordinates, with additional data variables that hold ancillary "formula terms" with which to calculate dimensional axis coordinates. It is used in atmosphere and ocean data sets.

Parametric vertical axes can only be read from file, not created from scratch.

Super classes

ncdfCF::CFObject -> ncdfCF::CFAxis -> ncdfCF::CFAxisNumeric -> CFAxisVertical

Active bindings

friendlyClassName

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

formula_terms

(read-only) A data.frame with the "formula_terms" to calculate the parametric axis values.

is_parametric

(read-only) Logical flag that indicates if the coordinates of the axis are parametric.

parametric_coordinates

(read-only) Retrieve the parametric coordinates of this vertical axis as a CFVariable.

computed_name

(read-only) The name of the computed parameterised coordinates. If the parameterised coordinates have not been computed yet the computed name is an empty string.

computed_units

(read-only) Return the units of the computed parameterised coordinates, if computed, otherwise return NULL. This will access the standard names table.

Methods

Public methods

• CFAxisVertical$new()

• CFAxisVertical$detach()

• CFAxisVertical$copy()

• CFAxisVertical$copy_with_values()

• CFAxisVertical$set_parametric_terms()

• CFAxisVertical$append()

• CFAxisVertical$subset()

• CFAxisVertical$subset_parametric_terms()

Inherited methods

• ncdfCF::CFObject$append_attribute()
• ncdfCF::CFObject$attribute()
• ncdfCF::CFObject$delete_attribute()
• ncdfCF::CFObject$dim()
• ncdfCF::CFObject$print_attributes()
• ncdfCF::CFObject$set_attribute()
• ncdfCF::CFObject$update_coordinates_attribute()
• ncdfCF::CFObject$write_attributes()
• ncdfCF::CFAxis$can_append()
• ncdfCF::CFAxis$configure_terms()
• ncdfCF::CFAxis$copy_terms()
• ncdfCF::CFAxis$peek()
• ncdfCF::CFAxis$shard()
• ncdfCF::CFAxis$write()
• ncdfCF::CFAxisNumeric$brief()
• ncdfCF::CFAxisNumeric$identical()
• ncdfCF::CFAxisNumeric$indexOf()
• ncdfCF::CFAxisNumeric$print()
• ncdfCF::CFAxisNumeric$range()
• ncdfCF::CFAxisNumeric$slice()

---

Method new()

Create a new instance of this class.

Usage

CFAxisVertical$new(
  var,
  values,
  start = 1L,
  count = NA,
  attributes = data.frame()
)

Arguments

var

The name of the axis when creating a new axis. When reading an axis from file, the NCVariable object that describes this instance.

values

Optional. The values of the axis in a vector. The values have to be numeric and monotonic. Ignored when argument var is a NCVariable object.

start

Optional. Integer index where to start reading axis data from file. The index may be NA to start reading data from the start.

count

Optional. Number of elements to read from file. This may be NA to read to the end of the data.

attributes

Optional. A data.frame with the attributes of the axis. When an empty data.frame (default) and argument var is an NCVariable instance, attributes of the axis will be taken from the netCDF resource.

---

Method detach()

Detach the parametric terms from an underlying netCDF resource.

Usage

CFAxisVertical$detach()

Returns

Self, invisibly.

---

Method copy()

Create a copy of this axis. The copy is completely separate from this instance, meaning that the copies of both this instance and all of its components are made as new instances.

Usage

CFAxisVertical$copy(name = "")

Arguments

name

The name for the new axis. If an empty string is passed, will use the name of this axis.

Returns

The newly created axis.

---

Method copy_with_values()

Create a copy of this axis but using the supplied values. The attributes are copied to the new axis. Boundary values, parametric coordinates and auxiliary coordinates are not copied.

After this operation the attributes of the newly created axes may not be accurate, except for the "actual_range" attribute. The calling code should set, modify or delete attributes as appropriate.

Usage

CFAxisVertical$copy_with_values(name = "", values)

Arguments

name

The name for the new axis. If an empty string is passed, will use the name of this axis.

values

The values to the used with the copy of this axis.

Returns

The newly created axis.

---

Method set_parametric_terms()

Set the parametric terms for this axis. The name and the terms have to fully describe a CF parametric vertical axis.

The terms must also agree with the other axes used by any data variable that refers to this axis. That is not checked here so the calling code must make that assertion.

Usage

CFAxisVertical$set_parametric_terms(sn, terms)

Arguments

sn

The "standard_name" of the parametric formulation. See the CF documentation for details.

terms

A data.frame with columns term, variable and param containing the terms of the formula to calculate the axis values. Column param has the references to the variables that hold the data for each term.

---

Method append()

Append a vector of values at the end of the current values of the axis. Boundary values are appended as well but if either this axis or the from axis does not have boundary values, neither will the resulting axis.

This method is not recommended for parametric vertical axes. Any parametric terms will be deleted. If appending of parametric axes is required, the calling code should first read out the parametric terms and merge them with the parametric terms of the from axis before setting them back for this axis.

Usage

CFAxisVertical$append(from)

Arguments

from

An instance of CFAxisVertical whose values to append to the values of this axis.

Returns

A new CFAxisVertical instance with values from this axis and the from axis appended.

---

Method subset()

Return an axis spanning a smaller coordinate range. This method returns an axis which spans the range of indices given by the rng argument. If this axis has parametric terms, these are not subset here - they should be separately treated once all associated axes in the terms have been subset. That happens automatically in CFVariable methods which call the subset_parametric_terms() method.

Usage

CFAxisVertical$subset(name = "", rng = NULL)

Arguments

name

The name for the new axis. If an empty string is passed (default), will use the name of this axis.

rng

The range of indices whose values from this axis to include in the returned axis. If the value of the argument is NULL, return a copy of the axis.

Returns

A new CFAxisVertical instance covering the indicated range of indices. If the value of the argument rng is NULL, return a copy of this axis as the new axis.

---

Method subset_parametric_terms()

Subset the parametric terms of this axis.

Usage

CFAxisVertical$subset_parametric_terms(
  original_axis_names,
  new_axes,
  start,
  count,
  aux = NULL,
  ZT_dim = NULL
)

Arguments

original_axis_names

Character vector of names of the axes prior to a modifying operation in the owning data variable

new_axes

List of CFAxis instances to use for the subsetting.

start

The indices to start reading data from the file, as an integer vector at least as long as the number of axis for the term.

count

The number of values to read from the file, as an integer vector at least as long as the number of axis for the term.

aux

Optional. List with the parameters for an auxiliary grid transformation. Default is NULL.

ZT_dim

Optional. Dimensions of the non-grid axes when an auxiliary grid transformation is specified.

Returns

Self, invisibly. The parametric terms will have been subset in this axis.

References

https://cfconventions.org/Data/cf-conventions/cf-conventions.html#parametric-vertical-coordinate https://www.myroms.org/wiki/Vertical_S-coordinate

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