Documents · Verb reference

variance

Return a variance reducer along dim with optional dimension retention.

Callable type: Grammar verb / pipe stage · Browse: Transform

Usage

from cubedynamics import verbs as v
v.variance(dim='time', *, over=None, keep_dim=True, skipna=True)

Arguments

Argument	Meaning	Default
dim	See implementation docstring below; no parameter-specific description supplied.	'time'
over	See implementation docstring below; no parameter-specific description supplied.	None
keep_dim	See implementation docstring below; no parameter-specific description supplied.	True
skipna	See implementation docstring below; no parameter-specific description supplied.	True

Accepts

An xarray DataArray or Dataset with the dimensions required by the selected operation. VirtualCube support is operation-specific; consult the implementation notes.

Returns

A callable stage. Applying it returns the transformed xarray object (or the supported VirtualCube result).

Order / grammar behavior

Apply before reductions that remove a required dimension. Choose the reduction dimensions explicitly; keep_dim=False removes reduced axes.

Minimal example

Run from the repository root after python -m pip install -e '.[vignettes]'. Uses the checked observational PRISM fixture; no network is required.

from pathlib import Path
import xarray as xr
import matplotlib.pyplot as plt
from cubedynamics import pipe, verbs as v

# Frozen, reviewed PRISM observations; run from the repository root.
path = Path("tests/fixtures/real_data/prism_boulder_january_2024.nc")
with xr.open_dataset(path, engine="scipy") as observed:
    cube = observed["tmax"].load()
assert cube.attrs["units"] == "degC"

result = (pipe(cube) | v.variance(dim="time", keep_dim=False)).unwrap()
# Variance has squared input units, even if inherited attributes say degC.
result.plot(cbar_kwargs={"label": "Temperature variance (°C²)"})
plt.show()

Works with