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Formula-based Calculation
Formula-based Calculation allows you to operate math, multivariate and neigbourhood functions on one or multiple grids. It also allows you to make queries (using the 'if-then-else' function). In fact all the functions from PCRaster can be used in this modeltype. For a description of the PCRaster functions we advise you to look in the PCRaster Manual.
You can add this modeltype with right click at a composite model or project and select 'Add New Model' and the select the Formula Based Function. Learn more about how to add models. To change the name of the model, type a name in the Properties window or in the Project Explorer. Open the window of the model by double clicking on the model in the Project Explorer, both windows look like the figure below. The numbers correspond with the steps to implement the response curve.
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User interface for the Fomula-based functions. The numbers correspond with the steps to implement the response curve.
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- Enter a name for the input variable.
- Double click at the field and select a map by browsing or by selecting a map from previous models. You can also use results from previous models by linking the maps in the Project Explorer.
- Name your output map and fill out the equation. Check if the equation is valid (when the equation is not valid an exclamation mark will be given or an error is given in the messages window)
The user interface will then look like the picture below:
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HABITAT uses a point '.' as a deliminator.
Note that x-values outside the range of the class division will result in a no-data value. Combining a no-data value with one of the input variables will also result in a no-data value. Therefore, it is very important to always check the range of the class division.