topic Re: Creating Field Calculator Expression in Geoprocessing Questions

Creating Field Calculator Expression

WahajHabib — Tue, 13 Jan 2015 09:06:12 GMT

Hi, I want to project population from an old census report.....the formula is as follows

population*(1+(growth rate/100))^16

I am trying this expression for calculating from attribute table but ITS NOT WORKING

[POP_B_SEX]*(1+ (4.33 / 100 ))Exp (16 )

Note : [POP_B_SEX] is the only column i am using from attribute table.

Re: Creating Field Calculator Expression

DanPatterson_Retired — Tue, 13 Jan 2015 09:26:40 GMT

Exponents aren't ^, they are **

Re: Creating Field Calculator Expression

WahajHabib — Tue, 13 Jan 2015 10:45:56 GMT

Yes but you see in the expression i am using "exp()"...wont they work?? and i tried with ** and doesn't work either....i guess there is something wrong with the expression....

Re: Creating Field Calculator Expression

Pieter_Geertvan_den_Beukel — Tue, 13 Jan 2015 10:49:26 GMT

Exp(16) means e^16 = 2.718282^16 = 8886111

You can simply use the ^ sign as in the formula.

Note: there is a difference between:

[POP_B_SEX]*(1+ (4.33 / 100 ))^16

and

([POP_B_SEX]*(1+ (4.33 / 100 )))^16

Re: Creating Field Calculator Expression

WahajHabib — Tue, 13 Jan 2015 10:55:10 GMT

Yeah i tried with ^ already but it doesn't work

Re: Creating Field Calculator Expression

Pieter_Geertvan_den_Beukel — Tue, 13 Jan 2015 11:23:21 GMT

The formula works for me....

Go in ArcMap to the Geoprocessing menu and click Geoprocessing Results. What is the error message that the Field Calculator returns?

To make the formula more simple:

(1+ (4.33 / 100 ))^16 = 1.97037

Your formula can be rewritten as:

[POP_B_SEX]*1.97037

Re: Creating Field Calculator Expression

WahajHabib — Tue, 13 Jan 2015 11:39:26 GMT

Yes it worked i had an extra square bracket..thanks