Ask A Cartographer

Quantifying values using graduated symbols

April 22 2010 | 0 comments
Categories: Symbology


I've tried searching the archives for an answer to my question, but not no avail. So, here goes.

What I am trying to do: is create a map which represents Indian Reserves based on the number of households they contain by using graduated symbols (symbology).

What I believe I need to do: is to create a new field in the attribute table with the household column - that much I believe is obvious.

My question: is what decides what is populated in the "Value:" field? To specify - I'm looking in the layer properties > Symbology > Quantities > Graduated symbols.

When I drop down the "Value" box, as seen in my attachment, only two of the columns represented in the Indian Reserves attribute table are shown, when several other columns exist in the Indian Reserve attribute table which contain number values.

My question is more of a "in theory" question. I'm wondering because I do not have rights to add any fields to our data; I will have to go through a higher power, so I want to be sure before I ask someone else to make any changes.

Thank you!

Mapping Center Answer:

You need to make sure that your "Household" field is a numeric field in order for it to be selectable in the Value Field drop down list.  If it is, then you can use it to create the graduated (or proportional) symbol map for your Indian Reserves. Valid numeric field data types include Short Integer, Long Integer, Single-precision floating-point number, and Double-precision floating-point number. When you create a new field, these appear in the Type drop down box as "Short Integer", "Long Integer", "Float", and "Double", respectively.

If you would like to post a comment, please login.

Contact Us | Legal | Privacy |