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I created a shape file a while ago with several (20+ polygons) in it. I was wondering if there is a way to symbolize these polygons with unique symbols.

Basically all I actually want to do is color them differently from each other, and I don't think I can do this when they are all in one file.

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Do your polygons have unique values? If so, you can go to the layer properties symbology tab, and symbolize by categories (unique values) –  Maksim Aug 20 at 19:08
    
If they were unique values, there would be a list of them in the table right? At the moment I only see one symbol. –  Katie C Aug 20 at 19:12
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select the field you want to symbolize by, then click "add all values". This should return different colored symbols –  Maksim Aug 20 at 19:13
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If you have multipart polygons, you may need to convert them to single part so they all have a unique ID. –  Luke Aug 20 at 19:46
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I think both answers provided already answer this question and would recommend that you reward one with an Accept tick and both with an upvote. If you have additional questions to ask then that can easily be done via a new question. –  PolyGeo Aug 21 at 1:35

2 Answers 2

up vote 1 down vote accepted

If you're using ArcGIS Desktop 10.0 software as the tag on your question suggests, all you would have to do is bring that shapefile into ArcMap. Then, right click on the resulting layer for that shapefile and select "Properties..." from the bottom of the context menu. Then go to the "Symbology" tab in the Layer Properties menu that should open up. On that tab select the "Categories" option and the "Unique Values" suboption. Then all you should have to do is select a field to use as the "Value Field". What this means is that each unique value in that field would be able to be drawn with a different color. So, if you had lets say 20 polygons and you had a field called region with the 20 polygons split between 3 different regions. You could symbolize on the region field and you would have 3 different colors.

However, if you are trying to draw every individual feature/polygon as a separate color, then you will want to make sure there is a field with a unique value for each feature (other than the ObjectID field). You could do this, if necessary, by adding a new field with field type LONG to the shapefile's attribute table and calculating that field to be the same as the ObjectID for each feature. Then you can go back to the symbology properties use that new field as the unique value field on which to symbolize. With that field selected, click add all values and, if necessary, change the color ramp to the desired color scheme. You can then, if needed, go back and change the colors for individual features by double clicking on their symbol.

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How do I calculate the LONG value as the same as the Id? –  Katie C Aug 20 at 19:21
    
You'd add a field to the attribute table and make sure to select Long Integer as the field type. Then if you had the attribute table open you could right click on that new field's field name and select "Field Calculator..." Then in the resulting dialog box just double click what is likely the first field listed (will probably be called ObjectID or OID or FID). Then click ok and it should fill that new field with the same value as your ID field. However, if you're not confident with the software, you might want to make a copy/backup of your data before adding or calculating any fields. –  John Aug 20 at 19:37
    
I've done this but it is still only creating another one field. The image may help. I'm testing it on a shapefile where there are 2 polygons. ![Test with 2 polygons][1] [1]: i.stack.imgur.com/ivPZS.png –  Katie C Aug 20 at 20:20
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Can you send a screen shot of the attribute table for that test data. I think that may help identify what's going wrong. Basically, ArcGIS lets you do symbology based on almost anything in the attribute table. So, what the symbology options show is going to be largely dependent on what values are in the attribute table. –  John Aug 20 at 20:24
    
Hi John, Sorry for the late reply. In my attribute table the Id values are all 0. I'm guessing this is a problem!? –  Katie C Aug 24 at 15:17

You can color different polygons in one shapefile differently - you don't need to put them in separate shapefiles. You do it through the Layer Properties and the Symbology Tab.

Once you are on the Symbology tab, you have a number of choices of how to symbolize your data. Which option is best depends on the type of data you are working with the information you have in your attribute table.

If there is a field in your attribute table that has a unique identifier for each polygon (which it sounds like from your question), and you would simply like each polygon to be a different color, you can choose Categories and then choose Unique Values.

Under Value Field, choose the field that contains the unique values and then click Add All Values at the bottom. Once you have this set, you can change the color ramp or modify the colors for individual values.

In this example, I symbolized a shapefile of Pennsylvania so that each county is a different color. This is what my Layer Properties window looks like: enter image description here

And this is what my results look like on my map: enter image description here

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