Field calculate n+2 into a new field

Question

I have a field of values 1,2,3,4,....400. I would like to calculate those values into a new field where the value of the SECOND record is 1+2, the third is 2+2,  etc, moving in what is basically a diagonal pattern down the list... I know how to do this in excel, but I don't want to take my .dbf out and mess with all that. I know there is a way in field calculator, it's just escaping me right now.

Here is an example of what I'm looking for,

LFLT868887898890899190

The field LT is already populated, and I want to calculate values into the LF field that are +2 of the value above it. Hope that makes sense?

Thanks!

Matt

matthewweber · Answer

Ok, so my example is a little off (I'm asking on behalf of a co-worker) as I was not sure what the table actually looked like.

The values in the table are not sequential (they are address blocks I believe?)

LFLT86889597112114140142174

So it's a bit more tricky...

AntGiles · Answer

Matthew,

Is your value in LF not just LT + 1?

open your attribute table, right click your LF header and select calculate field. In the field calculator double click your LT column so it appears in the box then manually add + 1.

JorgeOrellana · Answer

Just a thought, I don't know how to do that in arc, however, if you have a field that uniquely defines each feature i.e an ID number, export your DBF to excel, keep that unique ID, perform your excel magic, then join that excel sheet back to the feature class using that unique ID field, create a new field and calculate it based on the the one you created in Excel.  That's one way to approach it, I am sure someone with more programming saviness can help you with a script to do it.