# How can I reclassify a raster to floating point values?

I have a raster of landuse values that I need to reclassify into pollution concentration values. I have the pollution values in a separate table. They are decimal values (ex. 0.0056), and my landuse values are integers 1 through 6. I have a table mapping the landuse values to the pollution values.

I tried using the Reclass By Table tool, setting my pollution values as the "Output value field", but the tool description says that this field must be an integer field. How can I reclassify the values into decimal values? I feel like I must be missing a much easier, alternate solution.

My goal is to have a pollution concentration raster that I can use later in further calculations.

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## 3 Answers

1. Make sure your raster of landuse values has an attribute table
2. Add a join between landuse attribute table and pollution concentration table
3. Use the Lookup (Reclass) tool to create a new raster from the landuse raster with the values from the joined pollution concentration field.
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Why is step 3 needed? Can you not just create a new raster from the concentration values obtained in 2? (One used to be able to do that in older versions of Spatial Analyst.) – whuber May 17 '13 at 15:01
@whuber Because the old dot notation (raster.attribute) syntax that ESRI supported for years has been dropped as of ArcGIS 10. – Luke May 19 '13 at 11:34
Thanks, Luke (+1). – whuber May 19 '13 at 14:31
Thank you, this worked great! – Tanner May 20 '13 at 19:15

Int converts a floating point raster to a integer version as indicated. Float converts an integer raster to its floating point representation

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How does converting the landuse values into floating point help create a raster from values that are stored in a separate table? – Luke May 17 '13 at 3:42
allows for a join if scaled properly and appropriate field data exists for the join. I guess I assumed this would have been obvious beyond a 1st year GIS course...but point taken – Dan Patterson May 20 '13 at 20:38

You can try a simple way: multiply your concentrations by 10000 (or other value), to get all values as integers. Then you reclassify the raster, and then just divide output raster by the same 10000 using Raster calculator.

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