replace xr.ufuncs.log with np.log

Author: keewis

intermediate/hierarchical_computation.ipynb

@@ -137,7 +137,7 @@
    "source": [
     "## Applying functions designed for `Dataset` with `map_over_datasets`\n",
     "\n",
-    "What if we wanted to apply a element-wise function, for example to convert the data to log-space? For a `Dataset` or `DataArray`, we could just use {py:func}`xarray.ufuncs.log`, but that does not support `DataTree` objects, yet:"
+    "What if we wanted to apply a element-wise function, for example to convert the data to log-space? For a `DataArray` we could just use {py:func}`numpy.log`, but this is not supported for `DataTree` objects:"
    ]
   },
   {
@@ -147,16 +147,14 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "xr.ufuncs.log(tree)"
+    "np.log(tree)"
    ]
   },
   {
    "cell_type": "markdown",
    "id": "13",
    "metadata": {},
    "source": [
-    "Note how the result is a empty `Dataset`?\n",
-    "\n",
     "To map a function to all nodes, we can use {py:func}`xarray.map_over_datasets` and {py:meth}`xarray.DataTree.map_over_datasets`: "
    ]
   },
@@ -201,12 +199,7 @@
    "cell_type": "code",
    "execution_count": null,
    "id": "18",
-   "metadata": {
-    "tags": [
-     "raises-exception",
-     "hide-output"
-    ]
-   },
+   "metadata": {},
    "outputs": [],
    "source": [
     "tree.map_over_datasets(demean)"