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I have a column in my .dbf file that is a mixture of gradually increasing numbers but also a word for all of the items that don't match the criteria, for example:

**JUNIOR_PRI,N,4,2**
3.9
2.44
1.38
2.73
0
Non
Non
0

I didn't want to make the 'Non's a number, because then it would throw off my graduated color ramp if it took those into account; that's why I wanted to have the numbers ramp from yellow to blue, and then make the 'Non's all the same color -- like red. But when it goes into the GIS attribute table, it resets all my 'Non's to zeros. Is that because you can't mix numbers/words in a column?

And is it possible to do my initial thought -- or would I have to make another column with all the 'Non's in that one so I could overwrite the blanks from my "JUNIOR_PRI,N,4,2" column?

Thanks!

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1 Answer

Which desktop mapping application are you using?

ArcMap: you can just add all of your values EXCEPT for the Non's to your color ramp, and then click the check box next to (to un-select that box). EDIT: this only applies to categories.

If you're using graduated categories within ArcMap you can use "Data Exclusion" within the Classification properties box.

QGIS: the simplest way I can think of doing this is to give your "Non's" a numeric value well above all other values (e.g. 99999). Then "Classify" the graduated symbols in the Layer Properties dialogue. Then adjust your ranges to not include the outlier value you set for "Non's".

In general it isn't a great idea to mix data types in a single column. The practice could limit you later, making it difficult to move your data into a database such as PostgreSQL or any of the others.

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Thanks! I'm using QGIS on Mac OS X. Do those notes still apply? –  Ryan Mar 25 '13 at 0:17
    
@RyanO'Donnell not exactly. Please see my QGIS update in my answer. –  Paul Mar 25 '13 at 17:01
    
Thanks again! Your update is essentially what I tried. The headers in the DBF file alter this stuff as well, right? Whether it's "N,4,2" or "C,11" etc.? Assuming that "C" is when something's a 'string,' because it always reverts any words in that column to zero when it's "N." –  Ryan Mar 25 '13 at 17:07
    
The headers in your DBF file are the column names if I'm understanding your correctly. These should be the same values found the "Column" drop-down within the Layer Properties, Style tab. You'll be choosing a single column to base graduated symbols on. –  Paul Mar 25 '13 at 17:13
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