change polyval dim ordering (#6601)

Author: headtr1ck

xarray/core/computation.py

@@ -1909,7 +1909,7 @@ def polyval(
 
     # using Horner's method
     # https://en.wikipedia.org/wiki/Horner%27s_method
-    res = coeffs.isel({degree_dim: max_deg}, drop=True) + zeros_like(coord)
+    res = zeros_like(coord) + coeffs.isel({degree_dim: max_deg}, drop=True)
     for deg in range(max_deg - 1, -1, -1):
         res *= coord
         res += coeffs.isel({degree_dim: deg}, drop=True)

xarray/tests/test_computation.py

@@ -1951,7 +1951,7 @@ def test_where_attrs() -> None:
             xr.DataArray(
                 [[0, 1], [0, 1]], dims=("y", "degree"), coords={"degree": [0, 1]}
             ),
-            xr.DataArray([[1, 2, 3], [1, 2, 3]], dims=("y", "x")),
+            xr.DataArray([[1, 1], [2, 2], [3, 3]], dims=("x", "y")),
             id="broadcast-x",
         ),
         pytest.param(