windowed functions



I remember seeing some techniques for creating functions which are 0
outside of a certain window, or which "turn on" at a certain time. I
think I saw this relative to the interpolation code.

I have a problem where I am modelling a project in terms of costs
related to events. As the project progresses, people will be hired, or
during different phases, different consumables will be used etc.

i know that this is the kind of thing that is often done with excel,
but I am trying to do something a little fancier than what excel is
typically capable of. For example some events have probabilities of
occuring, and some events have durations modelled by random variables.

What facilities exist in maxima for defining functions which are
piecewise, or windowed? What sorts of operations can I do on such
functions?

Thanks!

-- 
Daniel Lakeland
dlakelan at street-artists.org
http://www.street-artists.org/~dlakelan