How do I resolve warning 002858?

Question

Hi, I'm trying to find the percent change of temperature using two climate projections with the formula %change=((new-old)/old)*100. When running it through "calculate field" this is what I have:

and I get this warning message with all of my values returned as null:

Any ideas?

bcgeogirl1 · Answer

This is how I fixed this problem when I had it.

%change=(((new or 0)-(old or 0))/(old or 0))*100

it puts in a 0 where the values are null. Hope it helps you

RyanBohan · Answer

Python treats null values as none.  And python can't add to nothing.
Attribute1 = null
Attribute2 =   5

Current State:
Attribute1 + Attribute1 = 
     none     +         5         = null

To handle Nulls:
Use or include a default value
(!Attribute1! or 0) + (!Attribute2! or 0) = 
               0               +                5               =  5

Or use arcade:
$feature.Attribute1 + $feature.Attribute2 = 
            null                 +                 5                 =  5

IssamAchour · Answer

yeah how to perform calculations and you have NULL values? i have these kinds of data since this information aren't reported so it must be involved in my geoprocessing work

how to deal with that using python?