topic Re: Selecting polygon with maximum value in Geoprocessing Questions

Selecting polygon with maximum value

PaulMcKenzie — Tue, 19 Feb 2013 09:20:14 GMT

Dear all

I am using a polygon shapefile and I want to select the polygon with the highest value. I am trying to implement this in ModelBuilder using ArcGIS Desktop v. 10.1. Ideally I want to select the maximum record and then use that selection to conduct additional analyses.

Any advice greatly appreciated.

Thank you,

Paul

Re: Selecting polygon with maximum value

RichardFairhurst — Tue, 19 Feb 2013 19:01:55 GMT

Dear all

I am using a polygon shapefile and I want to select the polygon with the highest value. I am trying to implement this in ModelBuilder using ArcGIS Desktop v. 10.1. Ideally I want to select the maximum record and then use that selection to conduct additional analyses.

Any advice greatly appreciated.

Thank you,

Paul

Generate a summary table and use the maximum value from it to do your selection. Subqueries are very limited, so summary tables are the way to go. A join back to the original to do selections allows you to continue the processing on the original dataset. Be aware that Maximum only works for numeric fields, not text or date fields. First works for text and date, but that dies not necessarily return the lowest alphabetic value or date value, just the first record in the table for the query criteria.

Re: Selecting polygon with maximum value

PaulMcKenzie — Wed, 20 Feb 2013 10:46:31 GMT

Many thanks for your reply. I had read about linking "Summary Statistics" with a tabular join. When you say

"join back to the original to do selections"

do you mean a tabular join? The problem is that after the summary statistics, all I have is the Maximum value and an ID value - is there a simple means by which I can also return the value of that polygon which has the maximum value?

Thanks again for your help,

Paul

Re: Selecting polygon with maximum value

JackBeers_III — Wed, 20 Feb 2013 11:09:36 GMT

Once you generate the summary table, use the Model Only Tool "Get Field Value." You can use this to return the value of the Summary Statistics Max Value for the field. You could then use the value to do other querys or analysis. It should look something like this:

[ATTACH=CONFIG]21980[/ATTACH]

Re: Selecting polygon with maximum value

RichardFairhurst — Wed, 20 Feb 2013 13:20:39 GMT

Many thanks for your reply. I had read about linking "Summary Statistics" with a tabular join. When you say

"join back to the original to do selections"

do you mean a tabular join? The problem is that after the summary statistics, all I have is the Maximum value and an ID value - is there a simple means by which I can also return the value of that polygon which has the maximum value?

Thanks again for your help,

Paul

Actually, normally for this type of analysis I do not use the ID value, because every record will be exported in the summary or an arbitrary min or max ID value will be outputted. I usually create a dummy field and make every record have the same value in that field (for example all records have 1 in that field). That is that case field that I summarize and tabular join to. The summary produces the Max value for the table or current selection. I use the join and a select by Attribute (Select from current selection if the summary was on a selection set) and find the record with a value equal to the max summary value (actually I really us a range relative to the Max value that is very small if the field is a double, i.e., Table.NumberField >= SummaryTable.MAX_NumberField - .0001 AND Table.NumberField <= SummaryTable.MAX_NumberField + .0001, because there can be slight rounding of the value during the summary that prevents the use of = ).