median_abs_deviation

xarray_einstats.stats.median_abs_deviation(da, dims=None, *, center=None, scale=1, nan_policy=None, **kwargs)

Wrap and extend scipy.stats.median_abs_deviation.

Usage examples available at Intro to the stats module.

All parameters take the same values and types as the scipy counterpart with the exception of scale. Here scale can also take DataArray values in which case, broadcasting is handled by xarray, as shown in the example.

Examples

Use a DataArray as scale.

import xarray as xr
from xarray_einstats import tutorial, stats
ds = tutorial.generate_mcmc_like_dataset(3)
s_da = xr.DataArray([1, 2, 1, 1], coords={"chain": ds.chain})
stats.median_abs_deviation(ds["mu"], dims="draw", scale=s_da)

<xarray.DataArray (chain: 4, team: 6)>
0.3468 0.4532 0.5054 0.876 0.6265 0.7342 ... 0.4382 0.5668 0.7103 0.2494 0.3485
Coordinates:
  * team     (team) <U1 'a' 'b' 'c' 'd' 'e' 'f'
  * chain    (chain) int64 0 1 2 3

xarray.DataArray

• chain: 4
• team: 6

• 0.3468 0.4532 0.5054 0.876 0.6265 ... 0.5668 0.7103 0.2494 0.3485

  array([[0.34676596, 0.45320205, 0.50539165, 0.8760277 , 0.62646553,
          0.73418378],
         [0.19816075, 0.29451242, 0.26859113, 0.35003099, 0.3795313 ,
          0.45268261],
         [0.41984653, 0.33699965, 0.55332021, 0.15398   , 0.3057486 ,
          0.39133525],
         [1.40888282, 0.43822259, 0.5668226 , 0.71029986, 0.24942531,
          0.34849295]])

• Coordinates: (2)
  • team
    (team)
    <U1
    'a' 'b' 'c' 'd' 'e' 'f'

    array(['a', 'b', 'c', 'd', 'e', 'f'], dtype='<U1')

  • chain
    (chain)
    int64
    0 1 2 3

    array([0, 1, 2, 3])

• Indexes: (2)
  • team
    PandasIndex

    PandasIndex(Index(['a', 'b', 'c', 'd', 'e', 'f'], dtype='object', name='team'))

  • chain
    PandasIndex

    PandasIndex(Index([0, 1, 2, 3], dtype='int64', name='chain'))

• Attributes: (0)

Note that this doesn’t work with the scipy counterpart because s_da can’t be broadcasted with the output:

from scipy import stats
stats.median_abs_deviation(ds["mu"], axis=1, scale=s_da)

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[2], line 2
      1 from scipy import stats
----> 2 stats.median_abs_deviation(ds["mu"], axis=1, scale=s_da)

File ~/checkouts/readthedocs.org/user_builds/xarray-einstats/envs/latest/lib/python3.10/site-packages/scipy/stats/_stats_py.py:3637, in median_abs_deviation(x, axis, center, scale, nan_policy)
   3634         med = np.expand_dims(center(x, axis=axis), axis)
   3635         mad = np.median(np.abs(x - med), axis=axis)
-> 3637 return mad / scale

File ~/checkouts/readthedocs.org/user_builds/xarray-einstats/envs/latest/lib/python3.10/site-packages/xarray/core/arithmetic.py:86, in SupportsArithmetic.__array_ufunc__(self, ufunc, method, *inputs, **kwargs)
     77     raise NotImplementedError(
     78         "xarray objects are not yet supported in the `out` argument "
     79         "for ufuncs. As an alternative, consider explicitly "
     80         "converting xarray objects to NumPy arrays (e.g., with "
     81         "`.values`)."
     82     )
     84 join = dataset_join = OPTIONS["arithmetic_join"]
---> 86 return apply_ufunc(
     87     ufunc,
     88     *inputs,
     89     input_core_dims=((),) * ufunc.nin,
     90     output_core_dims=((),) * ufunc.nout,
     91     join=join,
     92     dataset_join=dataset_join,
     93     dataset_fill_value=np.nan,
     94     kwargs=kwargs,
     95     dask="allowed",
     96     keep_attrs=_get_keep_attrs(default=True),
     97 )

File ~/checkouts/readthedocs.org/user_builds/xarray-einstats/envs/latest/lib/python3.10/site-packages/xarray/core/computation.py:1197, in apply_ufunc(func, input_core_dims, output_core_dims, exclude_dims, vectorize, join, dataset_join, dataset_fill_value, keep_attrs, kwargs, dask, output_dtypes, output_sizes, meta, dask_gufunc_kwargs, *args)
   1195 # feed DataArray apply_variable_ufunc through apply_dataarray_vfunc
   1196 elif any(isinstance(a, DataArray) for a in args):
-> 1197     return apply_dataarray_vfunc(
   1198         variables_vfunc,
   1199         *args,
   1200         signature=signature,
   1201         join=join,
   1202         exclude_dims=exclude_dims,
   1203         keep_attrs=keep_attrs,
   1204     )
   1205 # feed Variables directly through apply_variable_ufunc
   1206 elif any(isinstance(a, Variable) for a in args):

File ~/checkouts/readthedocs.org/user_builds/xarray-einstats/envs/latest/lib/python3.10/site-packages/xarray/core/computation.py:304, in apply_dataarray_vfunc(func, signature, join, exclude_dims, keep_attrs, *args)
    299 result_coords, result_indexes = build_output_coords_and_indexes(
    300     args, signature, exclude_dims, combine_attrs=keep_attrs
    301 )
    303 data_vars = [getattr(a, "variable", a) for a in args]
--> 304 result_var = func(*data_vars)
    306 out: tuple[DataArray, ...] | DataArray
    307 if signature.num_outputs > 1:

File ~/checkouts/readthedocs.org/user_builds/xarray-einstats/envs/latest/lib/python3.10/site-packages/xarray/core/computation.py:761, in apply_variable_ufunc(func, signature, exclude_dims, dask, output_dtypes, vectorize, keep_attrs, dask_gufunc_kwargs, *args)
    756     if vectorize:
    757         func = _vectorize(
    758             func, signature, output_dtypes=output_dtypes, exclude_dims=exclude_dims
    759         )
--> 761 result_data = func(*input_data)
    763 if signature.num_outputs == 1:
    764     result_data = (result_data,)

ValueError: operands could not be broadcast together with shapes (4,6) (4,)