The Function Editor is a visual programming language for building imagery and raster analysis workflows. An analysis workflow can be saved as a raster function template (RFT) that can be used to automate processes, or for rendering. You create and modify RFTs in the Function Editor pane. The Function Editor represents a function chain as a diagram that chains together function sequences using the output of one or more functions as the input to another function.
You can use various techniques to model a process that results in a RFT. For example, you can open the Function Editor and insert a raster variable and any functions. In this mode, no input data is connected to the chain so certain capabilities, such as previewing the result of a section of the processing chain, are disabled. Once data is connected to the processing chain, you can preview the results. You can save the raster function chain (now the RFT) and share and run it with different input datasets.
You can apply a raster function on a raster layer in the map using the Raster Functions pane, which creates a temporary raster layer in the map. You can also apply additional raster functions on the output layer. When you are finished applying functions, right-click the final output and click Save Function Chain or Edit Function Chain. The layer with the final function applied to it contains all of the previous functions with their parameter settings. Saving a layer's function chain removes the original input data and inserts raster variables that can be made public so the template can be used again with different data.
The function or raster function chain must have a final and single output to be valid.
You can do the following using the Function Editor:
- Visualize a workflow sequence as a diagram.
- Build an RFT by adding raster functions, raster variables, scalars, raster layers, datasets, other data types to the diagram, and connecting them to perform an analysis. The analysis can be performed on the current display extent or in a distributed manner using raster analysis on Portal for ArcGIS.
- Iteratively check parameters on a function raster layer's function chain. To interact with the display and the settings in the function chain, right-click the function raster layer in the Contents pane and click Edit Function Chain. When you make changes to parameters, click the Apply button on the Function Editor toolbar to refresh the layer to reflect the changes.
- Save a function raster layer's function chain as a RFT.
- Make a RFT usable to others by renaming functions, raster variables, and function variables.
The RFT below demonstrates a methodology for describing burn severity and the health of vegetation recovery using prefire and postfire imagery.
A RFT is composed of the following raster functions:
- Apparent Reflectance—Express the input imagery as albedo, which is the percentage of the available energy reflected by the planetary surface. It is commonly used by scientific users for complex modeling and technical remote sensing applications.
- Band Arithmetic—Perform a normalized burn ratio (NBR) index for prefire and postfire data from the output of albedo data.
- Minus—Create the change (or delta) in the NBR from the prefire NBR and postfire NBR.
- Remap—Define class break values for severity and vegetation health from the difference of the NBR.
- Attribute Table—Assign attributes and colors to the integer values created from each class defined in the Remap function.
Access the Function Editor
To build a RFT using the Function Editor, open a new editor window. Click the Function Editor button in the Analysis group on the Imagery tab. Then select and drag raster functions from the Raster Functions pane into the Function Editor pane.