Fix code for filtering with sel by calling compute.

Author: tomwhite

docs/examples/gwas_tutorial.ipynb

@@ -5904,7 +5904,7 @@
     }
    ],
    "source": [
-    "ds = ds.sel(samples=((ds.sample_dp_mean >= 4) & (ds.sample_call_rate >= 0.97)))\n",
+    "ds = ds.sel(samples=((ds.sample_dp_mean >= 4) & (ds.sample_call_rate >= 0.97)).compute())\n",
     "print(f\"After filter, {len(ds.samples)}/284 samples remain.\")"
    ]
   },
@@ -9219,7 +9219,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "ds = ds.sel(variants=((ds.variant_allele_frequency[:,1] > 0.01) & (ds.variant_hwe_p_value > 1e-6)))"
+    "ds = ds.sel(variants=((ds.variant_allele_frequency[:,1] > 0.01) & (ds.variant_hwe_p_value > 1e-6)).compute())"
    ]
   },
   {
@@ -11181,8 +11181,8 @@
    "source": [
     "# To run PCA we need to filter out variants with any missing alt allele counts\n",
     "# Or where the counts are zero for all samples\n",
-    "variant_mask = ((ds_pca.call_alternate_allele_count < 0).any(dim=\"samples\")) | \\\n",
-    "    (ds_pca.call_alternate_allele_count.std(dim=\"samples\") <= 0.0)\n",
+    "variant_mask = (((ds_pca.call_alternate_allele_count < 0).any(dim=\"samples\")) | \\\n",
+    "    (ds_pca.call_alternate_allele_count.std(dim=\"samples\") <= 0.0)).compute()\n",
     "ds_pca = ds_pca.sel(variants=~variant_mask)"
    ]
   },

docs/how_do_i.rst

@@ -135,11 +135,11 @@ Call :meth:`xarray.Dataset.sel` on the ``variants`` dimension:
 .. ipython:: python
 
     ds2 = sg.hardy_weinberg_test(ds)
-    ds2.sel(variants=(ds2.variant_hwe_p_value > 1e-2))
+    ds2.sel(variants=(ds2.variant_hwe_p_value > 1e-2).compute())
 
 .. note::
 
-   Filtering causes an eager Xarray computation.
+   The call to ``compute`` is needed to avoid an Xarray error.
 
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