extract: Avoid interpolation when everything is NaN (#53)

* Avoid interpolation when everything is NaN

* Add a test.

* black

src/dgpost/utils/extract.py

@@ -271,8 +271,12 @@ def _get_interp(spec, obj, at, ts):
         noms = unp.nominal_values(vals)
         sigs = unp.std_devs(vals)
         mask = ~np.isnan(noms) & ~np.isnan(sigs)
-        inoms = np.interp(ts, index[mask], noms[mask])
-        isigs = np.interp(ts, index[mask], sigs[mask])
+        if np.any(mask):
+            inoms = np.interp(ts, index[mask], noms[mask])
+            isigs = np.interp(ts, index[mask], sigs[mask])
+        else:
+            inoms = np.ones(len(ts)) * np.NaN
+            isigs = np.ones(len(ts)) * np.NaN
         colint.append(unp.uarray(inoms, isigs))
     return colnames, colint, colunits
 

tests/test_extract.py

@@ -290,3 +290,23 @@ def test_extract_df(infile, spec, outfile, datadir):
     print(f"{ref.head()=}")
     df.to_pickle(outfile)
     compare_dfs(ref, df)
+
+
+@pytest.mark.parametrize(
+    "inpath, outpath",
+    [
+        (  # ts0 - interpolate tables with nans
+            "nan.yaml",
+            "nan.df.pkl",
+        ),
+    ],
+)
+def test_extract_nan(inpath, outpath, datadir):
+    os.chdir(datadir)
+    dgpost.run(inpath)
+    df = pd.read_pickle(outpath)
+    print(f"{df.head()=}")
+    ref = pd.read_pickle(f"ref.{outpath}")
+    print(f"{ref.head()=}")
+    df.to_pickle(f"ref.{outpath}")
+    compare_dfs(ref, df)

tests/test_extract/nan.yaml

@@ -0,0 +1,23 @@
+version: "1.1"
+load:
+  - as: t1
+    path: nan.t1.pkl
+    type: table
+  - as: t2
+    path: nan.t2.pkl
+    type: table
+extract:
+  - into: df
+    from: t1
+    columns:
+      - key: xout
+        as: xout(t1)
+  - into: df
+    from: t2
+    columns:
+      - key: xout
+        as: xout(t2)
+save:
+  - table: df
+    as: nan.df.pkl
+