modified linearConvert to support numpy arrays.

metobs/data/__init__.py

 """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.