Calculate Field (Field Calculator)

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In GIS, Calculate Field is a tool used for calculations of information contained within attribute tables of data.

Attribute tables contain much of the non-geographic information related to layers of data used in ArcGIS. This information needs to be calculated at different times during data analysis to provide information that would be useful to users of ArcGIS. The Calculate Field tool is also known as the Field Calculator in the attribute table. The tool takes your mathematical formulas and transforms them into a computer language known as Python. The language is able to perform the calculations given and fill the related cells found in an attribute table. The mathematical problems that the field calculator (Calculate Field) range from a simple sum to complex problems.

For an example, this is a formula that assigns an importance (weight) to the prey types of the Canada Lynx by calculating a non-geographical data field with the Calculate Field calculator:

([HareUtil] * 0.70) + ([SquirrelUtil] * 0.25) + ([GrouseUtil] * 0.05)

There are many things you can do with the mathematical possibilities of the Calculate Field tool found in the Data Management toolbox.

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