Merge pull request #36 from nsidc/handle_lineslopecheck

Handle lineslopecheck

CHANGELOG.md

@@ -10,6 +10,9 @@
   that define e.g., valid ice masks. This code was very specific to NSIDC's
   internal infrastructure and unpublished data. It is now the responsibility of
   other programs utlizing this library to provide masks, input TBs, etc.
+* Replace `BootstrapAlgError` in `get_linfit` with a logged warning. Use default
+  slope and offset values instead of failing when there are less than 125 valid
+  pixels.
 
 # v0.2.0
 

pm_icecon/bt/compute_bt_ic.py

@@ -24,7 +24,7 @@
     WeatherFilterParamsForSeason,
 )
 from pm_icecon.constants import DEFAULT_FLAG_VALUES
-from pm_icecon.errors import BootstrapAlgError, UnexpectedSatelliteError
+from pm_icecon.errors import UnexpectedSatelliteError
 
 
 # TODO: this function very similar to `get_invalid_tbs_mask` in `compute_nt_ic`.
@@ -228,24 +228,32 @@ def get_linfit(
 
     num_valid_pixels = is_valid.sum()
     if num_valid_pixels <= 125:
-        raise BootstrapAlgError(f"Insufficient valid linfit points: {num_valid_pixels}")
+        bt_error_message = f"""
+        Insufficient valid linfit points: {num_valid_pixels}
+        """
+        logger.warning(f"Possible BootstrapAlgError: {bt_error_message}")
 
-    slopeb, intrca = np.polyfit(
-        x=tbx[is_valid],
-        y=tby[is_valid],
-        deg=1,
-    )
+        slopeb = lnline["slope"]
+        intrca = lnline["offset"]
+    else:
+        slopeb, intrca = np.polyfit(
+            x=tbx[is_valid],
+            y=tby[is_valid],
+            deg=1,
+        )
 
     if slopeb > max_slope:
-        raise BootstrapAlgError(
-            f"Line slope check failed. {slopeb=} > {max_slope=}. "
+        bt_error_message = f"""
+            Line slope check failed. {slopeb=} > {max_slope=}. "
             "This may need some additional investigation! The code from Goddard would"
             " fall back on defaults defined by the `iceline` parameter if this"
             " condition was met. However, it is probably better to investigate"
             " this situation and determine what to do on a case-by-case basis"
             ' rather than "silently" fall back on some default values. We are not'
             " sure how the default values of (`iceline`) were originally chosen."
-        )
+        """
+        logger.warning(f"Possible BootstrapAlgError:{bt_error_message}")
+        slopeb = max_slope
 
     fit_off = intrca + add
     fit_slp = slopeb