1 files changed, 7 insertions, 0 deletions
diff --git a/r_qtl/r_qtl2.py b/r_qtl/r_qtl2.py
index e4c1894..4f0ab2a 100644
--- a/r_qtl/r_qtl2.py
+++ b/r_qtl/r_qtl2.py
@@ -306,3 +306,10 @@ def raw_file_data(zipfilepath: Union[str, Path],
 def strip_comments(rawdata: Iterator[str], commentchar) -> Iterator[str]:
     """Remove comments from raw text."""
     return (line for line in rawdata if not line.startswith(commentchar))
+
+def missing_value_codes_to_none(value: str,
+                                nastrings: tuple[str, ...]) -> Optional[str]:
+    """
+    If 'value' is a missing value code, return `None`, otherwise return 'value'.
+    """
+    return value if value not in nastrings else None