153 subbeamnod routine cannot access plnum

src/dysh/fits/gbtfitsload.py

@@ -772,6 +772,7 @@ def subbeamnod(self, scan, bintable=None, **kwargs):
         kwargs_opts = {
             "ifnum": 0,
             "fdnum": 0,
+            "plnum": 1,
             "timeaverage": True,
             "weights": "tsys",  # or None or ndarray
             "calibrate": True,
@@ -781,6 +782,7 @@ def subbeamnod(self, scan, bintable=None, **kwargs):
         kwargs_opts.update(kwargs)
         ifnum = kwargs_opts["ifnum"]
         fdnum = kwargs_opts["fdnum"]
+        plnum = kwargs_opts["plnum"]
         docal = kwargs_opts["calibrate"]
         w = kwargs_opts["weights"]
         method = kwargs_opts["method"]
@@ -792,7 +794,12 @@ def subbeamnod(self, scan, bintable=None, **kwargs):
         if len(rx) > 1:
             raise TypeError("More than one receiver for the selected scan.")
         elif rx[0] == "Rcvr26_40":  # and df["DATE-OBS"][-1] < xxxx
-            # Switch the polarizations to match the beams.
+            # Switch the polarizations to match the beams
+            # for this receiver only because it has had its feeds
+            # mislabelled since $DATE.
+            # For the rest of the receivers the method should use
+            # the same polarization for the selected feeds.
+            # See also issue #160
             if fdnum == 0:
                 plnum = 1
             elif fdnum == 1:

src/dysh/spectra/tests/test_scan.py

@@ -137,7 +137,9 @@ def test_compare_with_GBTIDL(self, data_dir):
         # Generate the dysh result.
         # snodka-style. Need test for method='cycle'
         sdf = gbtfitsload.GBTFITSLoad(sdf_file)
-        sbn = sdf.subbeamnod(43, sig=None, cal=None, ifnum=0, fdnum=1, calibrate=True, weights="tsys", method="scan")
+        sbn = sdf.subbeamnod(
+            43, sig=None, cal=None, ifnum=0, fdnum=1, plnum=0, calibrate=True, weights="tsys", method="scan"
+        )
 
         # Load the GBTIDL result.
         hdu = fits.open(gbtidl_file)