Function _determine_cmap_params

xarray/plot/utils.py:161–328

Use some heuristics to set good defaults for colorbar and range. Parameters ---------- plot_data : Numpy array Doesn't handle xarray objects Returns ------- cmap_params : dict Use depends on the type of the plotting function

(
    plot_data,
    vmin=None,
    vmax=None,
    cmap=None,
    center=None,
    robust=False,
    extend=None,
    levels=None,
    filled=True,
    norm=None,
    _is_facetgrid=False,
)

def _determine_cmap_params(
    plot_data,
    vmin=None,
    vmax=None,
    cmap=None,
    center=None,
    robust=False,
    extend=None,
    levels=None,
    filled=True,
    norm=None,
    _is_facetgrid=False,
):
    """
    Use some heuristics to set good defaults for colorbar and range.

    Parameters
    ----------
    plot_data : Numpy array
        Doesn't handle xarray objects

    Returns
    -------
    cmap_params : dict
        Use depends on the type of the plotting function
    """
    if TYPE_CHECKING:
        import matplotlib as mpl
    else:
        mpl = attempt_import("matplotlib")

    if plot_data.dtype.kind == "m":
        unit, _ = np.datetime_data(plot_data.dtype)
        zero = np.timedelta64(0, unit)
    elif plot_data.dtype.kind == "M":
        unit, _ = np.datetime_data(plot_data.dtype)
        zero = np.datetime64(0, unit)
    else:
        zero = 0.0

    if isinstance(levels, Iterable):
        levels = sorted(levels)

    calc_data = np.ravel(plot_data[np.isfinite(plot_data)])

    # Handle all-NaN input data gracefully
    if calc_data.size == 0:
        # Arbitrary default for when all values are NaN
        calc_data = np.array(zero)

    # Setting center=False prevents a divergent cmap
    possibly_divergent = center is not False

    # Set center to 0 so math below makes sense but remember its state
    center_is_none = False
    if center is None:
        center = zero
        center_is_none = True