Formula Processor

From DGInsider Q1 2000/Q4 1999

The Formula Processor is an often overlooked part of EarthVision that can be used for a number of calculations, from simple “one-liners” to very complexly linked mathematical operations. Currently, over 90 different functions are available, divided into 14 classes including arithmetic, logarithmic, trigonimetric, relational, and many more. As functions are selected for use in a formula expression, help on their application automatically appears in the message area, offering an explanation as to what variables are needed for the calculation to proceed, and examples of usage.

You can select from a variety of file types and fields, either as formula components or objects of manipulation. Mathematical operations, symbols, and functions can also be incorporated into formulas by selection; a minimum of keyboard input is required.

One very nice aspect of working within the Formula Processor is the handling of variables. Variables may be file names, constants, or mathematical expressions. Variables may be either specific or generic. For variables not assigned a value in the original formula (i.e., generic variables), the Formula Processor pops up a window (shown below) that lists the undefined variables, prompting you to supply the missing pieces. Once completed, the calculation can proceed.

Another optional, but extremely helpful, feature (that is rarely used) is called “argument boxes.” If activated (by selecting Customize –> Argument Boxes), these windows prompt you for each parameter needed for a particular function within a formula. The output of each box may be sent to the main window (the default) or to another argument box, thus allowing nesting of operations.

You can also have a look at some other examples in the pages of your EarthVision User’s Guide (Volume 2, p. FP-19). Some of these examples might be immediately useful for the kind of work you do. We are also very interested in example formulas that you might be able to contribute to a formula library that other users can access; contact us at support@dgi.com or 510-522-0700.

 
[Home] [Corporate] [Events & News]
[EarthVision] [Support] [Services] [Contact Us]

Last updated: March 22, 2007