diff --git a/metobs/data/__init__.py b/metobs/data/__init__.py
index d955761cc379306fa413a1a0e2a2bf948a93cc29..6dc77a160a9582d4fdb1c1884c6ee2cac2871b49 100644
--- a/metobs/data/__init__.py
+++ b/metobs/data/__init__.py
@@ -1,4 +1,6 @@
 """Functions for calculating the dervied data.
+
+All linear conversion support ``numpy.ndarray`` objects.
 """
 __version__ = '$Revision: 1.15 $'
 #$Source: /cvsroot/TOOLS/dev/metobs/python/data/metobs/data/__init__.py,v $
@@ -237,7 +239,7 @@ def linearConvert(data, factor=1, offset=0):
     >>> linearConvert(1, 90, 10)
     100.0
     """
-    return float(data) * factor + offset
+    return data * float(factor) + offset
 
 def c2f (val):
     """Degrees celsius to fahrenheit.