Using Field calculator to populate field

Question

I have created a new field called "rank" in the attribute table of my soil data, and I want to populate my new "rank" field with a number of 1 to 5 based on attribute values from another field, for example: "if the attribute in the soil type field is peridotite, i want to fill the rank field with 1. and if the attribute in the soil type field is granodiorite i want to fill the rank field with 2" etc.

How would I go about doing this with field calculator? or is there another way I should be doing this.

Answer 1

In the field calculator (on the field you want to populate), select the Python parser at the top, check the Show Codeblock box and modify and use the code below to calculate your field:

def myrank(myfield):
    values = {'Peridotite': 1,
              'Granodiorite': 2,
              'Unobtanium': 3,
              'Somethingelseorite': 4 }

    if myfield in values:
        return values[myfield]

And then in the expression box at the bottom enter:

myrank(!SoilType!)

Update the values in values dictionary where the name is what you're looking for in your Soil Type field and the number is what you want to populate into your Rank field. Change myrank(!SoilType!) to match the field name of your Soil Type field (must be within two ! marks).