From 621e1d58d3fcce26d01c60b6e54123cde73432c5 Mon Sep 17 00:00:00 2001
From: David Schaefer <david.schaefer@ufz.de>
Date: Tue, 31 Aug 2021 13:54:58 +0200
Subject: [PATCH] [FIX] generic.flag generating new columns failed

---
 saqc/funcs/generic.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/saqc/funcs/generic.py b/saqc/funcs/generic.py
index 8dd387788..19738b671 100644
--- a/saqc/funcs/generic.py
+++ b/saqc/funcs/generic.py
@@ -255,7 +255,11 @@ def flag(
     if not np.issubdtype(mask.dtype, np.bool_):
         raise TypeError(f"generic expression does not return a boolean array")
 
-    m = ~_isflagged(flags[field], to_mask) & mask
-    flags[m, field] = flag
+    if field not in flags:
+        flags[field] = pd.Series(data=UNFLAGGED, index=mask.index, name=field)
+
+    mask = ~_isflagged(flags[field], to_mask) & mask
+
+    flags[mask, field] = flag
 
     return data, flags
-- 
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