issues: 271998358

As of xarray-0.10-rc1:

Works: ``` import xarray import scipy.stats a = xarray.DataArray([1,2], dims=['x'])

xarray.apply_ufunc(scipy.stats.norm.cdf, a, 0, 1)

<xarray.DataArray (x: 2)> array([ 0.841345, 0.97725 ]) Dimensions without coordinates: x ```

Broken: ``` xarray.apply_ufunc( scipy.stats.norm.cdf, a.chunk(), 0, 1, dask='parallelized', output_dtypes=[a.dtype] ).compute()

IndexError Traceback (most recent call last) <ipython-input-35-1d4025e1ebdb> in <module>() ----> 1 xarray.apply_ufunc(scipy.stats.norm.cdf, a.chunk(), 0, 1, dask='parallelized', output_dtypes=[a.dtype]).compute()

~/anaconda3/lib/python3.6/site-packages/xarray/core/computation.py in apply_ufunc(func, args, kwargs) 913 join=join, 914 exclude_dims=exclude_dims, --> 915 keep_attrs=keep_attrs) 916 elif any(isinstance(a, Variable) for a in args): 917 return variables_ufunc(args)

~/anaconda3/lib/python3.6/site-packages/xarray/core/computation.py in apply_dataarray_ufunc(func, args, kwargs) 210 211 data_vars = [getattr(a, 'variable', a) for a in args] --> 212 result_var = func(data_vars) 213 214 if signature.num_outputs > 1:

~/anaconda3/lib/python3.6/site-packages/xarray/core/computation.py in apply_variable_ufunc(func, args, kwargs) 561 raise ValueError('unknown setting for dask array handling in ' 562 'apply_ufunc: {}'.format(dask)) --> 563 result_data = func(input_data) 564 565 if signature.num_outputs > 1:

~/anaconda3/lib/python3.6/site-packages/xarray/core/computation.py in <lambda>(arrays) 555 func = lambda arrays: _apply_with_dask_atop( 556 numpy_func, arrays, input_dims, output_dims, signature, --> 557 output_dtypes, output_sizes) 558 elif dask == 'allowed': 559 pass

~/anaconda3/lib/python3.6/site-packages/xarray/core/computation.py in _apply_with_dask_atop(func, args, input_dims, output_dims, signature, output_dtypes, output_sizes) 624 for element in (arg, dims[-getattr(arg, 'ndim', 0):])] 625 return da.atop(func, out_ind, *atop_args, dtype=dtype, concatenate=True, --> 626 new_axes=output_sizes) 627 628

~/anaconda3/lib/python3.6/site-packages/dask/array/core.py in atop(func, out_ind, args, kwargs) 2231 raise ValueError("Must specify dtype of output array") 2232 -> 2233 chunkss, arrays = unify_chunks(args) 2234 for k, v in new_axes.items(): 2235 chunkss[k] = (v,)

~/anaconda3/lib/python3.6/site-packages/dask/array/core.py in unify_chunks(args, *kwargs) 2117 chunks = tuple(chunkss[j] if a.shape[n] > 1 else a.shape[n] 2118 if not np.isnan(sum(chunkss[j])) else None -> 2119 for n, j in enumerate(i)) 2120 if chunks != a.chunks and all(a.chunks): 2121 arrays.append(a.rechunk(chunks))

~/anaconda3/lib/python3.6/site-packages/dask/array/core.py in <genexpr>(.0) 2117 chunks = tuple(chunkss[j] if a.shape[n] > 1 else a.shape[n] 2118 if not np.isnan(sum(chunkss[j])) else None -> 2119 for n, j in enumerate(i)) 2120 if chunks != a.chunks and all(a.chunks): 2121 arrays.append(a.rechunk(chunks))

IndexError: tuple index out of range ```

Workaround: ``` xarray.apply_ufunc( scipy.stats.norm.cdf, a, kwargs={'loc': 0, 'scale': 1}, dask='parallelized', output_dtypes=[a.dtype]).compute()

<xarray.DataArray (x: 2)> array([ 0.841345, 0.97725 ]) Dimensions without coordinates: x ```