How do I make a new field based on an existing field?

Question

Hi,

I have a shapefile of the geology of the UK that contains lots of polygons for the different types of rocks. I want to group some of these polygons together but I'm not sure how.

There is a field called "Class" in my existing file and I want to create a new field called "NewClass". I basically want to do an if statement:

IF "Class" = '1A' or '2A', "NewClass" = 1
IF "Class" = '1B' or '2B', "NewClass" = 2
IF "Class" = '1C' or '2C' or '3', "NewClass" = 3

How do I do this in Arc10 (windows 7)

Thanks

MarcinGasior · Answer

@LeoNard,
I'm afraid your code also won't work.
To test two or more parameters the syntax is:if RouteType == 'I' or RouteType == 'PKWY':
    return 70
    ...

#alternatively:

if RouteType in ('I', 'PKWY'):
    return 70
    ...

LeonardWilliamson · Answer

You need 2 equal signs instead of just one when checking the attributedef speed(RouteType):
if RouteType == 'I', 'PKWY':
return 70
elif RouteType == 'US', 'KY':
return 55
elif RouteType == 'CNTY':
return 45
elif RouteType == 'CITY', 'OTHR':
return 35
elif RouteType == 'PRIV':
return 25

SudeshnaGhosh · Answer

Hi I did run this, it is as follows:
CODE:

def speed(RouteType):
   if RouteType = 'I', 'PKWY':
        return 70
   elif RouteType = 'US', 'KY':
        return 55
   elif RouteType = 'CNTY':
       return 45
   elif RouteType = 'CITY', 'OTHR':
       return 35
   elif RouteType = 'PRIV':
       return 25

THEN Speed_Limit =

speed (!ROUTE_TYPE!)

However, I am getting an error "ERROR 00989: Python syntax error: Parsing error <type 'exceptions.SyntaxError'>: invalid syntax (line 2)"
Is there any mistake?

Thanks
Sudeshna