1

I want to create a thematic map in arcmap using the fields NAME and NOTES for 3 categories of polygons:

  1. where the name cell is null
  2. where the name cell is filled
  3. where the name cell is null, but it has the note "NUME EBRAICA", which means "name in hebrew"; this note appears only to the polygons where the name cell is empty.

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Any suggestions, please? Everything I've tried didn't work.

4

It is a very similar question to this.

In layer properties go to Symbology tab. Then choose Categories and Unique Values, Many Fields. Choose your both fields and add values to the table with particular symbol and color to all of your combinations.

  • 2
    Do not use add all in above approach. Add blank - blank, blank- ebratica. 3 rd class - all other values – FelixIP Jul 17 '15 at 21:26
  • That worked for me. But is it possible to use more than 3 fields for a thematic map? Why this limit?. – panda Jul 17 '15 at 21:55
  • Because number of permutations can be too big – FelixIP Jul 17 '15 at 22:01
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    @IoanaIstrate-Ciobanu no, you're limited to three fields. I don't know of an official reason, but consider that each unique combination of values in all fields gets its own symbol. 10 possible values in each of 3 fields yields a possible 720 unique combinations. You can see how you could quickly arrive at a great number of unique symbols - possibly more than the software can handle. – Chris W Jul 17 '15 at 22:10
2

Classes 1 and 2 are easy and straightforward. It's the 3rd conditional that makes things a bit tricky. I'd approach this with a definition query for simplicity. You could do all three separate, but I'll just suggest two.

Add your polygon layer once and symbolize it on the name field. You'll choose null for one value and leave the other to 'all other values'. This should give you the first two classes you want.

Then copy that layer, or add your data a second time. In the properties dialog for the new layer, go to the Definition Query tab and build the appropriate SQL expression to show only polys where name is null. Then on the symbology tab you can once again do categories but this time on the notes field. You'll set the value "NUME EBRAICA" to be your third symbol, and then change the 'all other values' symbology to be blank (as in no fill, no outline). This should then show only polygons where the name field is null and the note field has that value. With this layer above your other in the table of contents, you should have the three color map you want. You could also do a custom symbol for this layer so it's stripes or something and the same null color from the other layer would show through if you wanted.

This method doesn't require modifying the data if that would be an issue, and it should be a bit simpler than trying to symbolize on multiple fields since with that method you must symbolize all possible combinations (though you can group them to only have to set the symbology once).

1

I would recommend using a classification (Classify tool) for those 3 categories (name=null, name=filled, and notes=filled). This should be made into a new field within the attribute table. Example: name cell null and notes cell null is 0, name cell filled, notes cell null is 1, and name cell null and notes cell is filled is 2. You can use something other than numbers, that is just an example.

From here you can edit the symbology section of the layer to display what you want it to. Choose the symbology to represent the new field, that should help you separate the different categories. You can also tamper with the label properties to display the actual names.

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    Not sure there's a tool for classification of vector data, but it could certainly be done with the field calculator. – Chris W Jul 17 '15 at 21:25

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