fix

rowers/dataroutines.py

@@ -2302,7 +2302,7 @@ def dataplep(rowdatadf, id=0, inboard=0.88, forceunit='lbs', bands=True, barchar
         finish = df['finish']
         peakforceangle = df['peakforceangle']
         arclength = (inboard - 0.05) * (np.radians(finish) - np.radians(catch))
-        if arclength.mean() > 0:
+        if arclength.mean() is not None and arclength.mean() > 0:
             drivelength = arclength
         else:
             drivelength = data['drivelength']