topic Calculating field values only for appropriate features using ArcMap in Data Management Questions

Calculating field values only for appropriate features using ArcMap

RafaelMichael — Sat, 01 Feb 2020 18:50:57 GMT

Just like in the attached picture. I would like to calculate the value for the field "indeks_star" with the formula: indeks_star =[TOT_65__] / [TOT_0_14] * 100

And for features where in the field TOT_0_14 occurs 0 or in [TOT_65__] occurs 0, I would like the value -9999 to appear in the field indeks_star.

What formula to enter in the field calculator to simultaneously calculate all values for the field indeks_star?

Re: Calculating field values only for appropriate features using ArcMap

DavidPike — Sun, 12 Dec 2021 08:16:39 GMT

Hello again,

on field calculator, select Python as your parser (top radio button) and select 'show codeblock' which appears in the middle of the window.

where it has whitespace below 'pre-logic script code' insert the code below

def percentage(field1, field2) :

    if field1 != 0 and field2 != 0 :
        return ( (float(field1) / float(field2) ) * 100.0)

    else :
        return -9999‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

in the bottom bit of whitespace it should have something like 'indeks_star =' above it in the greyed out area. in the whitespace type out this:

percentage(!TOT_0_14!, !TOT_65!)

Re: Calculating field values only for appropriate features using ArcMap

RafaelMichael — Sat, 01 Feb 2020 19:47:40 GMT

shouldn't it be the other way around?

no
percentage(!TOT_0_14!, !TOT_65!) but percentage( !TOT_65!, !TOT_0_14!)

Re: Calculating field values only for appropriate features using ArcMap

DavidPike — Sat, 01 Feb 2020 19:55:46 GMT

Depends which way round you want it really, in your question you wanted _14/_65 ?

Re: Calculating field values only for appropriate features using ArcMap

RafaelMichael — Sat, 01 Feb 2020 20:03:40 GMT

I just edited the post now. Sorry for the mistake. Should be [TOT_65__] / [TOT_0_14] * 100

so it will be percentage( !TOT_65__!, !TOT_0_14!) ?

Re: Calculating field values only for appropriate features using ArcMap

DavidPike — Sat, 01 Feb 2020 20:17:50 GMT

Yeh should work

Re: Calculating field values only for appropriate features using ArcMap

RafaelMichael — Sat, 01 Feb 2020 20:27:39 GMT

many features calculated correctly, many -9999(no problem), but there are also many cases when the value of the field indeks_star should be calculated, but a value of 0 for this field is created.

Re: Calculating field values only for appropriate features using ArcMap

DavidPike — Sat, 01 Feb 2020 20:50:23 GMT

Maybe it's doing integer division. I'll amend the code now

Re: Calculating field values only for appropriate features using ArcMap

RafaelMichael — Sat, 01 Feb 2020 21:04:26 GMT

all values seem fine now. thank you!!! I have to create one more field and calculate one more formula, will you wait 5 minutes? I'm already putting it here

Re: Calculating field values only for appropriate features using ArcMap

RafaelMichael — Sat, 01 Feb 2020 21:25:17 GMT

AProchow = (TOT_65/TOT)*100

if field TOT is 0 or field TOT_65__ is 0 then field AProchow equals -9999

Re: Calculating field values only for appropriate features using ArcMap

DavidPike — Sat, 01 Feb 2020 21:31:51 GMT

I'm going to let you suggest the code then we can look at it.

Re: Calculating field values only for appropriate features using ArcMap

RafaelMichael — Sun, 12 Dec 2021 08:16:41 GMT

def percentage(field1, field2) :

    if field1 != 0 and field2 != 0 :
        return ( (float(field1) / float(field2) ) * 100.0)

    else :
        return -9999

percentage( !TOT_65__!, !TOT!) ?

Re: Calculating field values only for appropriate features using ArcMap

DavidPike — Sat, 01 Feb 2020 21:41:02 GMT

Re: Calculating field values only for appropriate features using ArcMap

RafaelMichael — Sat, 01 Feb 2020 21:43:51 GMT

values seem correct, thanks for everything!

Re: Calculating field values only for appropriate features using ArcMap

JoshuaBixby — Mon, 03 Feb 2020 18:29:46 GMT

This type of basic calculation with a Null or zero check can be accomplished on one line using a Python conditional expressions, a.k.a., ternary operators,

-9999 if !TOT! == 0 else !TOT_65!/float(!TOT!)*100‍