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<P> Implements a time-series simulation engine suitable for time-series gene
    expression
    studies. The simulation engine is constructed as follows. First, an update
    graph
    is constructed using the LagGraph class. An update graph is a time series
    graph
    where causal edges go from variables (called factors here to avoid
    ambiguity)
    at previous time lags >= 1 to the current time lag == 0. This update graph
    is
    then used to construct an update function--that is, a function that is
    capable
    of taking a history of time series coltData and generating the next step by way
    of simulation. Once the update graph has been constructed, a compatible
    history
    nodes is constructed using it. A history nodes maintains internally a
    history
    array--ie a 2D array (m factors x n + 1 time lags, where n is the maximum
    lag
    of the update graph) of coltData. The history nodes is capable of updating this
    array to the next step. Simulation can then be done by repeatedly calling
    the
    update() method on this history nodes..

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    <I>Note.</I>The word "factor" is used instead of "variable" in the package
    to avoid confusion. It's possible in a time series graph to
    consider each variable at a given time lag (or even at a given
    time step) as a variable in its own right. Therefore, the
    word "factor" is used to indicate a variable which is not
    considered at a time lag or time step but rather as stable
    through time.
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