issue_comments: 275960531

See http://stackoverflow.com/questions/40179593/how-to-get-the-coordinates-of-the-maximum-in-xarray for examples of how to do this with the current version of xarray. @MaximilianR's answer using where is pretty clean, but maybe not the most efficient or exactly what we want. (I think it breaks in a few edge cases, such as if the max value appears multiple times, or the array is all NaN.)

@jcmgray Your proposal looks pretty close to me. But to handle higher dimension arrays, instead of take(y, indx), I think you need to NumPy style fancy indexing, y[indx,]. That doesn't work with dask, so you'll need to write a function function that uses dask.array.map_blocks when necessary.

I think something like the following would work: ```python def _index_from_1d_array(array, indices): return array[indices,]

def gufunc_idxmax(x, y, axis=None): # note: y is always a numpy.ndarray, because IndexVariable objects # always have their data loaded into memory indx = argmax(x, axis) func = functools.partial(_index_from_1d_array, y)

if isinstance(array, dask_array_type):
    import dask.array as da
    return da.map_blocks(func, indx, dtype=indx.dtype)
else:
    return func(indx)

```