File:Elutin1a4tori.jpg
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Summary
| Title / Description
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Iterations of the logistic transfer function $f(x)=4x(1\!-\!x)$ (shown qith thick black line) $y=f^c(x)$ for $c=$ 0.2, 0.5, 0.8, 1, 1,5 . Function $f$ is iterated $c$ times; however, the number $c$ of iterations has no need to be integer. This pic was generated with the "universal" algorithm that evaluates the iterations of more general function $f_u(x)=u~x~ (1\!-\!x)$; see [1]. Namely for $u\!=\!4$, the iterates can be expressed through the elementary function, and such a plot can be generated, for example, in Mathematica with very simple code: F[c_, z_] = 1/2 (1 - Cos[2^c ArcCos[1 - 2 z]]) Plot[{F[1.5, x], F[1, x], F[.8, x], F[.5, x], F[.2, x]}, {x, 0, 1}] In order to keep the code short, the colors are not adjusted. The representation above can be obtained from the representation of the superfunction $F$ and the Abel function $G$: : $f^c(z)=F(c+G(z))$ at : $F(z)= \frac{1}{2}(1−\cos(2z))$ : $G(z)=F^{-1}(z)=\log_2(\arccos(1\!−\!2z))$ |
|---|---|
| Citizendium author
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Dmitrii Kouznetsov |
| Date created
|
March 2011 |
| Country of first publication
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Japan |
| Notes
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More superfunctions represented through elementary functions can be found in
[2]. Copyleft 2011 by Dmitrii Kouznetsov. The free use is allowed. References
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| Other versions
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http://tori.ils.uec.ac.jp/TORI/index.php/File:Elutin1a4tori.jpg |
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