I'm having trouble understanding how to implement a multiple regression equation in ArcGIS 10.3. I've already performed the regression in SAS and have the necessary coefficients, and so I don't need to redo an analysis with one of the Modeling Spatial Relationship tools in ArcGIS. I simply need to create a new raster that is derived from my existing equation based on values from 3 different input rasters. I've examined the Combine Tool, but that converts my numeric values to integers. Weighted overlay apparently is based on ranking data. What am I missing?