cf.Field

---

class cf.Field(properties=None, source=None, copy=True, _use_data=True)

Bases: cf.mixin.propertiesdata.PropertiesData, cfdm.field.Field

A field construct of the CF data model.

The field construct is central to the CF data model, and includes all the other constructs. A field corresponds to a CF-netCDF data variable with all of its metadata. All CF-netCDF elements are mapped to a field construct or some element of the CF field construct. The field construct contains all the data and metadata which can be extracted from the file using the CF conventions.

The field construct consists of a data array and the definition of its domain (that describes the locations of each cell of the data array), field ancillary constructs containing metadata defined over the same domain, and cell method constructs to describe how the cell values represent the variation of the physical quantity within the cells of the domain. The domain is defined collectively by the following constructs of the CF data model: domain axis, dimension coordinate, auxiliary coordinate, cell measure, coordinate reference and domain ancillary constructs.

The field construct also has optional properties to describe aspects of the data that are independent of the domain. These correspond to some netCDF attributes of variables (e.g. units, long_name and standard_name), and some netCDF global file attributes (e.g. history and institution).

NetCDF interface

The netCDF variable name of the construct may be accessed with the nc_set_variable, nc_get_variable, nc_del_variable and nc_has_variable methods.

The selection of properties to be written as netCDF global attributes may be accessed with the nc_global_attributes, nc_clear_global_attributes and nc_set_global_attribute methods.

Initialization

Parameters

properties: dict, optional

Set descriptive properties. The dictionary keys are property names, with corresponding values. Ignored if the source parameter is set.

Parameter example:

properties={'standard_name': 'air_temperature'}

Properties may also be set after initialisation with the set_properties and set_property methods.

source: optional

Initialize the properties, data and metadata constructs from those of source.

copy: bool, optional

If False then do not deep copy input parameters prior to initialization. By default arguments are deep copied.

Inspection

Methods

dump	A full description of the field construct.
identity	Return the canonical identity.
identities	Return all possible identities.

Attributes

construct_type	Return a description of the construct type.
id	A canonical identity.

Selection

Methods

match_by_identity	Whether or not the construct identity satisfies conditions.
match_by_naxes	Whether or not the data has a given dimensionality.
match_by_ncvar	Whether or not the netCDF variable name satisfies conditions.
match_by_property	Whether or not properties satisfy conditions.
match_by_rank	Whether or not the number of domain axis constructs satisfies conditions.
match_by_units	Whether or not the construct has given units.
match_by_construct	Whether or not there are particular metadata constructs.

Properties

Methods

del_property	Remove a property.
get_property	Get a CF property.
has_property	Whether a property has been set.
set_property	Set a property.
properties	Return all properties.
clear_properties	Remove all properties.
set_properties	Set properties.

Attributes

add_offset	The add_offset CF property.
calendar	The calendar CF property.
cell_methods	Return cell method constructs.
comment	The comment CF property.
Conventions	The Conventions CF property.
_FillValue	The _FillValue CF property.
flag_masks	The flag_masks CF property.
flag_meanings	The flag_meanings CF property.
flag_values	The flag_values CF property.
history	The history CF property.
institution	The institution CF property.
leap_month	The leap_month CF property.
leap_year	The leap_year CF property.
long_name	The long_name CF property.
missing_value	The missing_value CF property.
month_lengths	The month_lengths CF property.
references	The references CF property.
scale_factor	The scale_factor CF property.
source	The source CF property.
standard_error_multiplier	The standard_error_multiplier CF property.
standard_name	The standard_name CF property.
title	The title CF property.
units	The units CF property.
valid_max	The valid_max CF property.
valid_min	The valid_min CF property.
valid_range	The valid_range CF property.

Units

override_units	Override the units.
override_calendar	Override the calendar of date-time units.

Units

The cf.Units object containing the units of the data array.

Data

Methods

del_data	Remove the data.
get_data	Return the data.
has_data	Whether a data has been set.
set_data	Set the field construct data.
del_data_axes	Remove the keys of the domain axis constructs spanned by the data of the field or of a metadata construct.
get_data_axes	Return the keys of the domain axis constructs spanned by the data of a metadata construct.
has_data_axes	Whether the domain axis constructs spanned by the data of the field or of a metadata construct have been set.
set_data_axes	Set the domain axis constructs spanned by the data of the field or of a metadata construct.

Attributes

array	A numpy array deep copy of the data array.
data	The Data object containing the data array.
datetime_array	An independent numpy array of date-time objects.
datum	Return an element of the data array as a standard Python scalar.
dtype	The numpy data type of the data array.
ndim	The number of dimensions in the data array.
shape	A tuple of the data array’s dimension sizes.
size	The number of elements in the data array.
varray	A numpy array view of the data array.

Rearranging elements

anchor	Roll a cyclic axis so that the given value lies in the first coordinate cell.
flatten	Flatten axes of the field.
flip	Flip (reverse the direction of) axes of the field.
insert_dimension	Insert a size 1 axis into the data array.
roll	Roll the field along a cyclic axis.
squeeze	Remove size 1 axes from the data.
swapaxes	Interchange two axes of the data.
transpose	Permute the axes of the data array.
unsqueeze	Insert size 1 axes into the data array.

Data array mask

count	Count the non-masked elements of the data.
count_masked	Count the masked elements of the data.
fill_value	Return the data array missing data value.

binary_mask	A binary (0 and 1) missing data mask of the data array.
hardmask	Whether the mask is hard (True) or soft (False).
mask	The mask of the data array.
mask_invalid	Mask the array where invalid values occur.

Changing data values

__setitem__	Called to implement assignment to x[indices]=value
indices	Create indices that define a subspace of the field construct.
mask_invalid	Mask the array where invalid values occur.
subspace	Create a subspace of the field construct.
where	Assign to data elements depending on a condition.

Miscellaneous data operations

Methods

chunk	Partition the data array.
close	Close all files referenced by the field.
cyclic	Set the cyclicity of an axis.
files	Return the names of any files containing parts of the data array.

Metadata constructs

Methods

construct	Select a metadata construct by its identity.
construct_key	Select the key of a metadata construct by its identity.
del_construct	Remove a metadata construct.
get_construct	Return a metadata construct.
has_construct	Whather a metadata construct exisits.
set_construct	Set a metadata construct.
replace_construct	Replace a metadata construct.
del_data_axes	Remove the keys of the domain axis constructs spanned by the data of the field or of a metadata construct.
get_data_axes	Return the keys of the domain axis constructs spanned by the data of a metadata construct.
has_data_axes	Whether the domain axis constructs spanned by the data of the field or of a metadata construct have been set.
set_data_axes	Set the domain axis constructs spanned by the data of the field or of a metadata construct.
auxiliary_coordinate	Return an auxiliary coordinate construct, or its key.
cell_measure	Select a cell measure construct by its identity.
cell_method	Select a cell method construct by its identity.
coordinate	Return a dimension coordinate construct, or its key.
coordinate_reference	Return a coordinate reference construct, or its key.
dimension_coordinate	Return a dimension coordinate construct, or its key.
domain_ancillary	Return a domain ancillary construct, or its key.
domain_axis	Return a domain axis construct, or its key.
domain_axis_key	Return the key of the domain axis construct that is spanned by 1-d coordinate constructs.
domain_axis_position	Return the position in the data of a domain axis construct.
field_ancillary	Return a field ancillary construct, or its key.

Attributes

constructs	Return the metdata constructs.
auxiliary_coordinates	Return auxiliary coordinate constructs.
cell_measures	Return cell measure constructs.
cell_methods	Return cell method constructs.
coordinates	Return dimension and auxiliary coordinate constructs.
coordinate_references	Return coordinate reference constructs.
dimension_coordinates	Return dimension coordinate constructs.
domain_ancillaries	Return domain ancillary constructs.
domain_axes	Return domain axis constructs.
axes	Return domain axis constructs.
field_ancillaries	Return field ancillary constructs.

Domain

Methods

get_domain

Return the domain.

Attributes

domain

Return the domain.

Miscellaneous

Methods

copy	Return a deep copy of the field construct.
equals	Whether two instances are the same.
compress	Compress the field construct.
convert	Convert a metadata construct into a new field construct.
creation_commands	Return the commands that would create the field construct.
radius	Return the radius used for calculating cell areas in spherical polar coordinates.
uncompress	Uncompress the construct.
cf.Field.concatenate	Join a sequence of fields together.

Attributes

Flags	A Flags object containing self-describing CF flag values.
has_bounds	Whether or not there are cell bounds.
isauxiliary	True if the variable is an auxiliary coordinate object.
isdimension	True if the variable is a dimension coordinate object.
ismeasure	True if the variable is a cell measure object.
rank	The number of axes in the domain.
T	True if and only if the data are coordinates for a CF ‘T’ axis.
X	Always False.
Y	Always False.
Z	Always False.

NetCDF

Methods

nc_del_variable	Remove the netCDF variable name.
nc_get_variable	Return the netCDF variable name.
nc_has_variable	Whether the netCDF variable name has been set.
nc_set_variable	Set the netCDF variable name.
nc_global_attributes	Return the selection of properties to be written as netCDF global attributes.
nc_clear_global_attributes	Remove the selection of properties to be written as netCDF global attributes.
nc_set_global_attribute	Select a property to be written as a netCDF global attribute.
nc_set_global_attributes	Set properties to be written as netCDF global attributes.
dataset_compliance	A report of problems encountered whilst reading the field construct from a dataset.

Domain axes

autocyclic	Set dimensions to be cyclic.
axes	Return domain axis constructs.
cf.Field.axes_sizes
axis	Alias of cf.Field.domain_axis.
axis_name	Return the canonical name for an axis.
axis_size	Return the size of a domain axis construct.
cyclic	Set the cyclicity of an axis.
data_axes	Return the domain axes for the data array dimensions.
iscyclic	Returns True if the given axis is cyclic.
item_axes	Return the axes of a domain item of the field.
items_axes	Return the axes of items of the field.
period	Return the period of an axis.

Subspacing

__getitem__	Return a subspace of the field construct defined by indices.
subspace	Create a subspace of the field construct.
indices	Create indices that define a subspace of the field construct.

Mathematical operations

Trigonometrical and hyperbolic functions

arcsinh	Take the inverse hyperbolic sine of the data element-wise.
arctan	Take the trigonometric inverse tangent of the data element-wise.
cos	Take the trigonometric cosine of the data, element-wise.
cosh	Take the hyperbolic cosine of the data array in place.
sin	The trigonometric sine of the data, element-wise.
sinh	Take the hyperbolic sine of the data array in place.
tan	The trigonometric tangent of the data, element-wise.
tanh	Take the hyperbolic tangent of the data array.

Rounding and truncation

ceil	The ceiling of the data, element-wise.
clip	Limit the values in the data.
floor	Floor the data array, element-wise.
rint	Round the data to the nearest integer, element-wise.
round	Round the data to the given number of decimals.
trunc	Truncate the data, element-wise.

Statistical collapses

collapse	Collapse axes of the field.
cell_area	Return a field containing horizontal cell areas.
max	The maximum of the data array.
mean	The unweighted mean the data array.
mid_range	The unweighted average of the maximum and minimum of the data array.
min	The minimum of the data array.
range	The absolute difference between the maximum and minimum of the data array.
sample_size	The number of non-missing data elements in the data array.
sum	The sum of the data array.
sd	The unweighted sample standard deviation of the data array.
var	The unweighted sample variance of the data array.
weights	Return weights for the data array values.

Exponential and logarithmic functions

exp	The exponential of the data, element-wise.
log	The logarithm of the data array.

Derivatives

derivative

Return the derivative along the specified axis.

Convolution filters

convolution_filter

Return the field convolved along the given axis with the specified filter.

Cumulative sums

cumsum

Return the field cumulatively summed along the given axis.

Binning operations

bin	Collapse the data values that lie in N-dimensional bins.
digitize	Return the indices of the bins to which each value belongs.
percentile	Compute percentiles of the data along the specified axes.

Data array operations

Adding and removing elements

unique

The unique elements of the data.

Miscellaneous data array operations

chunk	Partition the data array.
isscalar	True if the data array is scalar.

Regridding operations

regridc	Return the field with the specified Cartesian axes regridded onto a new grid.
regrids	Return the field regridded onto a new latitude-longitude grid.

Date-time operations

day	The day of each date-time data array element.
datetime_array	An independent numpy array of date-time objects.
hour	The hour of each date-time data array element.
minute	The minute of each date-time data array element.
month	The month of each date-time data array element.
second	The second of each date-time data array element.
year	The year of each date-time data array element.

convert_reference_time

Convert reference time data values to have new units.

Logic functions

Truth value testing

all	Test whether all data elements evaluate to True.
any	Test whether any data elements evaluate to True.

Comparison

allclose	Test whether all data are element-wise equal to other, broadcastable data.
equals	Whether two instances are the same.
equivalent	True if two fields are equivalent, False otherwise.
cf.Field.equivalent_data
cf.Field.equivalent_domain

Set operations

unique

The unique elements of the data.

Aliases

Methods

aux	Alias for cf.Field.auxiliary_coordinate.
auxs	Alias for cf.Field.auxiliary_coordinates.
axis	Alias of cf.Field.domain_axis.
coord	Alias for cf.Field.coordinate.
coords	Alias for cf.Field.coordinates.
dim	Alias for cf.Field.dimension_coordinate.
dims	Alias for cf.Field.dimension_coordinates.
domain_anc	Alias for cf.Field.domain_ancillary.
domain_ancs	Alias for cf.Field.domain_ancillaries.
field_anc	Alias for cf.Field.field_ancillary.
field_ancs	Alias for cf.Field.field_ancillaries.
item	Alias for cf.Field.construct`.
items	Alias for c.Field.constructs.filter_by_data.
key	Alias for cf.Field.construct_key.
match	Alias for match_by_identity.
measure	Alias for cf.Field.cell_measure.
measures	Alias for cf.Field.cell_measures.
ref	Alias for cf.Field.coordinate_reference.
refs	Alias for cf.Field.coordinate_references.

Attributes

dtarray

Alias for datetime_array.

Arithmetic and comparison operations

Arithmetic, bitwise and comparison operations are defined on a field construct as element-wise operations on its data which yield a new field construct or, for augmented assignments, modify the field construct’s data in-place.

Relational operators

__lt__	The rich comparison operator <
__le__	The rich comparison operator <=
__eq__	The rich comparison operator ==
__ne__	The rich comparison operator !=
__gt__	The rich comparison operator >
__ge__	The rich comparison operator >=

Binary arithmetic operators

__add__	The binary arithmetic operation +
__sub__	The binary arithmetic operation -
__mul__	The binary arithmetic operation *
__div__	The binary arithmetic operation /
__truediv__	The binary arithmetic operation / (true division)
__floordiv__	The binary arithmetic operation //
__pow__	The binary arithmetic operations ** and pow
__mod__	The binary arithmetic operation %

Binary arithmetic operators with reflected (swapped) operands

__radd__	The binary arithmetic operation + with reflected operands
__rsub__	The binary arithmetic operation - with reflected operands
__rmul__	The binary arithmetic operation * with reflected operands
__rdiv__	The binary arithmetic operation / with reflected operands
__rtruediv__	The binary arithmetic operation / (true division) with reflected operands
__rfloordiv__	The binary arithmetic operation // with reflected operands
__rpow__	The binary arithmetic operations ** and pow with reflected operands
__rmod__	The binary arithmetic operation % with reflected operands

Augmented arithmetic assignments

__iadd__	The augmented arithmetic assignment +=
__isub__	The augmented arithmetic assignment -=
__imul__	The augmented arithmetic assignment *=
__idiv__	The augmented arithmetic assignment /=
__itruediv__	The augmented arithmetic assignment /= (true division)
__ifloordiv__	The augmented arithmetic assignment //=
__ipow__	The augmented arithmetic assignment **=
__imod__	The binary arithmetic operation %=

Unary arithmetic operators

__neg__	The unary arithmetic operation -
__pos__	The unary arithmetic operation +
__abs__	The unary arithmetic operation abs

Binary bitwise operators

__and__	The binary bitwise operation &
__or__	The binary bitwise operation |
__xor__	The binary bitwise operation ^
__lshift__	The binary bitwise operation <<
__rshift__	The binary bitwise operation >>

Binary bitwise operators with reflected (swapped) operands

__rand__	The binary bitwise operation & with reflected operands
__ror__	The binary bitwise operation | with reflected operands
__rxor__	The binary bitwise operation ^ with reflected operands
__rlshift__	The binary bitwise operation << with reflected operands
__rrshift__	The binary bitwise operation >> with reflected operands

Augmented bitwise assignments

__iand__	The augmented bitwise assignment &=
__ior__	The augmented bitwise assignment |=
__ixor__	The augmented bitwise assignment ^=
__ilshift__	The augmented bitwise assignment <<=
__irshift__	The augmented bitwise assignment >>=

Unary bitwise operators

__invert__

The unary bitwise operation ~

Special

Methods

__deepcopy__	Called by the copy.deepcopy function.
__getitem__	Return a subspace of the field construct defined by indices.
__repr__	Called by the repr built-in function.
__str__	Called by the str built-in function.