Spei, proper use of loc parameter in scipy dists

CHANGES.rst

@@ -44,6 +44,8 @@ Breaking changes
 * `black` formatting style has been updated to the 2024 stable conventions. `isort` has been added to the `dev` installation recipe. (:pull:`1626`).
 * The indice and indicator for ``winter_storm`` has been removed (deprecated since `xclim` v0.46.0 in favour of ``snd_storm_days``). (:pull:`1565`).
 * `xclim` has dropped support for `scipy` version below v1.9.0 and `numpy` versions below v1.20.0. (:pull:`1565`).
+* For generic function ``select_resample_op`` and ``core.units.to_agg_units``, operation "sum" will now return the same units as the input, and not implicitly be translated to an "integral". (:issue:`1645`, :pull:`1649`).
+* `lmoments3` was removed as a dependency of `xclim` due to incompatible licensing (GPLv3 vs `xclim`'s Apache 2.0). Depending on the outcome of efforts to modify the licensing of `lmoments3`, this change may eventually be reverted. See `Ouranosinc/lmoments3#12 <https://github.com/Ouranosinc/lmoments3/issues/12>`_. See also the "frequency analysis" notebook for an example on how to continue using the probability weighted moments method for fitting distributions. (:issue:`1620`, :pull:`1644`).
 * Argument `offset` is removed  from ``xclim.indices.standardized_precipitation_evapotranspiration_index``. This will slightly change results when using SPEI with default values (:issue:`1477`  :pull:`1653`).
 
 Bug fixes

xclim/indices/stats.py

@@ -776,7 +776,7 @@ def standardized_index(
     da: xr.DataArray,
     freq: str | None,
     window: int,
-    dist: str,
+    dist: str | scipy.stats.rv_continuous | None,
     method: str,
     cal_start: DateStr | None,
     cal_end: DateStr | None,
@@ -785,6 +785,11 @@ def standardized_index(
 ) -> xr.DataArray:
     r"""Standardized Index (SI).
 
+    This computes standardized indices which measure the deviation of  variables in the dataset compared
+    to a reference distribution. The reference is a statistical distribution computed with fitting parameters `params`
+    over a given calibration period of the dataset. Those fitting parameters are obtained with
+    ``xclim.standardized_index_fit_params``.
+
     Parameters
     ----------
     da : xarray.DataArray
@@ -795,9 +800,9 @@ def standardized_index(
     window : int
         Averaging window length relative to the resampling frequency. For example, if `freq="MS"`,
         i.e. a monthly resampling, the window is an integer number of months.
-    dist : {"gamma", "fisk"}
+    dist : str or rv_continuous
         Name of the univariate distribution. (see :py:mod:`scipy.stats`).
-    method : {'APP', 'ML'}
+    method : str
         Name of the fitting method, such as `ML` (maximum likelihood), `APP` (approximate). The approximate method
         uses a deterministic function that doesn't involve any optimization.
     cal_start : DateStr, optional