Evaluation modes

Revision as of 19:33, 2 February 2007 by Lchrisman (talk | contribs) (in progress)
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(in progress) Analytica's computational engine evaluates expressions. When you view a result for a variable, Analytica evaluates the expression stored in that variable's definition attribute.

When you view a "Mid" result, Analytica evaluates the definition in Mid-Mode. When you view any of the other result views (Mean, Stats, Bands, PDF or Prob Mass, CDF or Cum Prob, or Sample), Analytica evaluates the result in Sample-mode. Sometimes the terms prob-mode or probability-mode are used synonymously to Sample-mode. Some expression return different results in Mid-Mode and Sample-Mode. These are usually expressions that have probabilistic results.

A is a function that returns a median value when evaluated in Mid-mode, and a sample array indexed by the Run Index when evaluated in Sample-mode.

The evaluation mode (Mid or Sample) can change as sub-expressions are evaluated. For example, the Mean function computes the mean of an uncertain quantity. In order to do this, Mean requires the sample value. So, when Mean(X+Y) is evaluated in Mid-Mode, Analytica first evaluates X+Y in Sample-Mode, then passes this value to the Mean function.

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