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I have two tables: one in Excel and one in .txt format. I need to move these into ArcMap 10.1 and combine them with a polygon shapefile of counties in a state. However I don't know how to do this.

Afterwards I need to calculate the mean center of the population of the state by using the data provided by the two tables. Each table consists of a list of the counties and the population of each county for different years. The fields are the years and the first field states the county names.

I've tried merging the two tables in Excel and then importing my table in ArcMap, then when I try to do a join between the shapefile and the table I get null values where the attached table values should be.

Can someone explain to be how I would exactly get this data joined to the polygon shapefile? I'm fairly new to GIS so please be mindful of my lack of knowledge on this subject when answering.

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  • determining the mean center of population for the state would be a lot more meaningful using census blocks or even tracts than counties. You have the right idea regarding joining the tables. You need some sort of identifier to connect your table to the county features (like a FIPS id). Note that the type of data matters for that identifier so that if it is a text field in the counties feature class, it needs to be text in your table (and if a number, then it needs to be a number). – jbchurchill Sep 23 '14 at 13:46
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If you are attempting to join data held in Excel I suspect this the root of your problem. Firstly fields must be of the same data type for a join, you cannot join a string to a number field. Which field are you using to join with? In Excel you can have a field that appears to hold ID numbers but is in fact a string field, hence nothing ever joins.

If they are both text then are they the same case? "UK" will not join with "uk".

Lots of people like to make Excel pretty by putting in blank rows and lining up things, this is utterly useless! Your top row needs to be the header with no unusual characters and no spaces. So if you had "temp (c)" this needs to be "temp_c".

I would start looking at how you have set up Excel .

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