File:Elutin1a4tori.jpg: Difference between revisions
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== Summary == | == Summary == | ||
{{Image_Details|user-pd | {{Image_Details|user-pd | ||
|description = Iterations of the [[logistic transfer function]] <math>f(x)=4x(1\!-\!x)</math> (shown with thick black line) <math>y=f^c(x)</math> for <math>c=</math> 0.2, 0.5, 0.8, 1, 1,5 . Function <math>f</math> is iterated <math>c</math> times; however, the number <math>c</math> of iterations has no need to be [[integer]]. This pic was generated with the "universal" algorithm that evaluates the iterations of more general function <math>f_u(x)=u~x~ (1\!-\!x)</math>; see <ref name="logistic"> http://www.springerlink.com/content/u712vtp4122544x4/ D.Kouznetsov. Holomorphic extension of the logistic sequence. Moscow University Physics Bulletin, 2010, No.2, p.91-98. </ref>. Namely for <math>u\!=\!4</math>, the iterates can be expressed through the elementary function, and such a plot can be generated, for example, in [[Mathematica]] with very simple code: | |description = Iterations of the [[logistic transfer function]] <math>f(x)=4x(1\!-\!x)</math> (shown with thick black line): <math>y=f^c(x)</math> for <math>c=</math> 0.2, 0.5, 0.8, 1, 1,5 . Function <math>f</math> is iterated <math>c</math> times; however, the number <math>c</math> of iterations has no need to be [[integer]]. This pic was generated with the "universal" algorithm that evaluates the iterations of more general function <math>f_u(x)=u~x~ (1\!-\!x)</math>; see <ref name="logistic"> http://www.springerlink.com/content/u712vtp4122544x4/ D.Kouznetsov. Holomorphic extension of the logistic sequence. Moscow University Physics Bulletin, 2010, No.2, p.91-98. </ref>. Namely for <math>u\!=\!4</math>, 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]]) | 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}] | Plot[{F[1.5, x], F[1, x], F[.8, x], F[.5, x], F[.2, x]}, {x, 0, 1}] |
Revision as of 00:43, 18 May 2011
Summary
Title / Description
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Iterations of the logistic transfer function (shown with thick black line): for 0.2, 0.5, 0.8, 1, 1,5 . Function is iterated times; however, the number of iterations has no need to be integer. This pic was generated with the "universal" algorithm that evaluates the iterations of more general function ; see [1]. Namely for , 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 code above can be obtained from the representation of the superfunction and the Abel function
at Failed to parse (syntax error): {\displaystyle F(z)= \frac{1}{2}(1−\cos(2z))} Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle G(z)=F^{-1}(z)=\log_2(\arccos(1\!−\!2z))} |
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Citizendium author
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Dmitrii Kouznetsov |
Date created
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March 2011 |
Country of first publication
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Japan |
Notes
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Expressions for the more general case are suggested in the article Logistic sequence.
More superfunctions represented through elementary functions can be found in [2]. Copyleft 2011 by Dmitrii Kouznetsov. Previously, this image appeared at http://tori.ils.uec.ac.jp/TORI/index.php/File:Elutin1a4tori.jpg ; 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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