On Fri, 2 May 2008, Angus McMorland wrote: > How about multiplying two Boltzmann terms together, ala: > > f(x) = 1/(1+exp(-(x-flex1)/tau1)) * 1/(1+exp((x-flex2)/tau2))
> You'll find if your two flexion points get too close together, the peak > will drop below the maximum for each individual curve, but the transition > will be continuous. Angus, With an x range from 0.0-100.0 (and the flexion points at 25.0 and 75.0), the above formula provides a nice bell-shaped curve from x=0.0 to x=50.0, and a maximum y of only 0.25 rather than 2.0. Modifying the above so the second term is subtracted from 1 before the multiplication, or by negating the exponent in the second term, yields only the first half: the ascending 'S' curve from 0-50. Thanks, Rich -- Richard B. Shepard, Ph.D. | Integrity Credibility Applied Ecosystem Services, Inc. | Innovation <http://www.appl-ecosys.com> Voice: 503-667-4517 Fax: 503-667-8863 _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
