indices.generic.doymax | doymin crashes when it encounters an All-Nan slice.

[RondeauG]

Setup Information

• Xclim version: v0.53.2

Description

xclim.indices.generic.doymax and xclim.indices.generic.doymin will raise a ValueError when they encounter an All-NaN slice, instead of simply returning a NaN.

Steps To Reproduce

import numpy as np
import xclim as xc
from xclim.testing.helpers import test_timeseries as timeseries

da = timeseries(
    np.repeat(np.nan, 1000),
    variable="tas",
    as_dataset=False
)
da.attrs["units"] = "m3 s-1"

# This crashes
xc.indicators.land.doy_qmax(da)

# This also crashes, and is the line used in `xclim.indices.generic.doymax`
da.argmax(dim="time")

# This also crashes, and is the function used by xarray when calling `da.argmax()`.
np.nanargmax(da.values)

# This returns 0
np.argmax(da.values)

Additional context

While this could seem like a strange thing to want to support, this can hapen fairly often when trying to process multiple stations at the same time (with different start/end dates for their operations). I expect that this would also happen fairly often with freq=MS | QS.

Contribution

• I would be willing/able to open a Pull Request to address this bug.

Code of Conduct

• I agree to follow this project's Code of Conduct