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PCRaster Website: Arrays Home Introduction Demo Downloads Documentation Support Courses Case studies Publications Projects People Links Department of Physical Geography Faculty of Geosciences Utrecht University The Netherlands Arrayed variables in PCRcalc Document version 4.0 By Willem van Deursen and Cees Wesseling, PCRaster Environmental Software VOF DISCLAIMER: The new features documented here are considered to be in alpha status. Things may change a bit in later releases. This release is intended to get feedback from users who want to apply these features. As always, we do welcome ideas and suggestions but for alpha software we can not garantuee the same level of support as for our regular software. Introduction PCRcalc allows for the construction of arrayed variables. The concept reduces the need for copying parts of the script several times to create similar behavior for a number of species or related components. The clearest need for this type of concept comes from simulating ecosystem dynamics, where the main goal is to model the interaction between species. Although ecosystem dynamics deals with a number of species, these species demonstrate similar (not identical) behavior. Until the introduction of arrayed variables, this type of models was constructed in PCRaster by copying the section that described the first species and substitute the parameter values for the second species. This approach yields a script that can become very long and is becoming more and more difficult to maintain. Changes made to the process descriptions have to be implemented in several similar sections, and parameter values are scattered throughout the script. The use of arrayed variables improves this situation because it allows for a structured way of describing the similar processes in the different species, and it allows for the species to be initialized from external files. Identification and access to arrayed variables The introduction of the arrayed variables is straightforward. In the binding section of the script we need to identify the arrayed variable, while in the initial and dynamic section we need to use the foreach construct to iterate over the array. Furthermore, we developed index... functions to create an interface to external parameter files. The identification of the arrayed variables is in the binding section. binding PlantSpecies = [ Species1, Species2, http://pcraster.geog.uu.nl/documentation/manual_updates/ArraysInCalc.html (1 van 7) [3/2/2005 5:04:25 PM]
