Network dataset - Costs: How to create a evaluator expression referencing a field of the feature class

ConnieSu

Hello! I have a network dataset and I want to create a evaluator expression in "Costs" referencing a field of the feature class. Can somebody help me, please?

These are my current costs of the ND.

For the edges feature class "PNL2017_Rodovias_Completo", I would like to create a expression like this:

if(TYPENO=="7001"):
    return 0.069001*[Shape]
else:
    return 0.039429*[Shape]

 And for the junctions feature class "PNL2017_Suporte_Pontos_Rodo", I would like something like this:

if(TYPENO=="7001"):
    return 17.1361
else:
    return 35.18

Could you please help me? 

Thanks and regards!

Melinda Morang

You can do this with a field script evaluator.  Those evaluator dialogs are a little hard to use, though, so I can see why you need a hint!

First, for the evaluator you want to update, double click in the Value column until you see the box on the far right with the green X.

You'll get a pop-up box where you can create an expression for the field script evaluator.  You will want something like this:

Basically the Result box calls a custom-defined function called get_value() and passes the TYPENO and Shape field values to it.  The ! surrounding the field names is what's used for Python evaluators.  I'm using Python instead of VBScript because it's easier to code in (for me), and VBScript evaluators will be deprecated soon.

Here's the code for the codeblock:

def get_value(typeno, shape):
    if typeno == "7001":
        return 0.069001 * shape
    else:
        return 0.039429 * shape

 

Your expression for the junctions source will be very similar, but you won't need to pass the Shape field into the function.