[pstricks] Drawing S- and Z-Curves

[Rich Shepard]

On Tue, 21 Apr 2009, Michael Sharpe wrote:

> Both S-curves and Z-curves, as I know them, are defined by functions known
> to Postscript, so there is no need for Bezier approximations.

Michael,

   Oh. Guess I need to go find those. I vaguely recall it takes extra code to
place raw PS in the PSTricks .tex file. Is that correct?

> Of course, both those terms have multiple meanings, but I assume that
> Z-curve means a normal density curve (two parameters) and S-curve means a
> logistic curve (3 parameters.)

   In the realm of approximate reasoning models, a Z-curve is 1-S-curve. In
the .eps example I attached to my initial post, the left-most curve is a
Z-curve, the middle ones are normal/bell/Gaussian curves, and the right-most
is an S-curve. A Z-curve starts at y=1.0 and ends at y=0.0; an S-curve is
the opposite.

   Yes, different disciplines assign different meaning to the same term.

Rich

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