Working with external data

Working with external data

Simile provides a mechanism to enable data to be associated with model variables when you run the model, rather than having the values built into the model itself. The mechanism is based on a file called the scenario file. For each variable, this file contains either the actual values, or a reference to another file which contains the values. This other file can be a text file, in CSV (comma-separated value) format containing the data, either in a single column or as a grid of values. Alternatively it can be an image file, with each pixel standing for a data value according to its colour, or any of a range of other raw data formats.

A "scenario" is then the set of all the values required for the model to run. These include parameter values, site conditions, initial values for compartments, time-series data (e.g. a rainfall record), etc.

This section first provides an overview of the scenario file mechanism, outlining its motivation and capabilities. We then look at the two types of input parameters, the elements by which external data comes into the model. The File Parameter and Table Data dialogues are used to set up the relationshop between data files and parameters. We show how to create .csv files, which are the most widely used kind of data file. We then discuss how modifying parameterization fits into the model edit/run cycle, and provide some worked examples.

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