computing the iterated exp(x)-1
#4
It seems clear to me that these polynomials should be stored in a matrix. You have two sets of variables: n^0, n^1, n^2, ..., and z^0, z^1, z^2, ..., and a you have one coefficient for each combination, so long as the degree of n is less than the degree of z.

Depending on whether you make the z's a row vector or a column vector, you'll either have an upper triangular matrix or a lower triangular matrix. Once in that format, it should be much easier to pick out the patterns, and it should provide an effective viewpoint to assess convergence.

At any rate, I'm not terribly concerned if the radius of convergence is goes to 0 as the number of terms goes to infinity. There should still be a limit that is well-behaved, even if it means taking the limit as z goes to 0, with an integer iteration count that goes to infinity to get us back up the vicinity of z=1.

This is essentially what I did with my cheta function, but with linear interpolation. With a higher degree interpolation function based on the power series derived here (e.g., the first 20 terms should converge very nicely for z <0.01), convergence should be even more well-behaved, and by extension, the limit that much more defensible. Assuming the limit is defensible, then less accuracy could be acceptable by using a non-limited approximation.

And this is assuming the radius of convergence indeed goes to 0. I don't have access to Baker's proof, so I don't have a lot to go on at the moment.
~ Jay Daniel Fox
Reply


Messages In This Thread
computing the iterated exp(x)-1 - by Daniel - 08/13/2007, 10:47 PM
RE: computing the iterated exp(x)-1 - by andydude - 08/16/2007, 01:28 AM
RE: computing the iterated exp(x)-1 - by jaydfox - 08/16/2007, 06:51 AM
RE: computing the iterated exp(x)-1 - by bo198214 - 08/16/2007, 07:48 AM
RE: computing the iterated exp(x)-1 - by andydude - 08/17/2007, 08:44 PM
RE: Iterability of exp(x)-1 - by bo198214 - 08/13/2007, 10:50 PM
RE: Iterability of exp(x)-1 - by Daniel - 08/14/2007, 06:51 PM
RE: Iterability of exp(x)-1 - by jaydfox - 08/14/2007, 01:01 AM
RE: Iterability of exp(x)-1 - by Gottfried - 08/14/2007, 12:45 PM
RE: Iterability of exp(x)-1 - by bo198214 - 08/14/2007, 04:11 PM
RE: Iterability of exp(x)-1 - by Gottfried - 08/14/2007, 04:35 PM
RE: Iterability of exp(x)-1 - by jaydfox - 08/14/2007, 02:42 AM
RE: Iterability of exp(x)-1 - by Gottfried - 08/14/2007, 03:08 AM
RE: Iterability of exp(x)-1 - by jaydfox - 08/14/2007, 05:09 AM
RE: Iterability of exp(x)-1 - by Gottfried - 08/14/2007, 05:09 AM

Possibly Related Threads…
Thread Author Replies Views Last Post
  4 hypothesis about iterated functions Shanghai46 11 13,146 04/22/2023, 08:22 PM
Last Post: Shanghai46
  Question about the properties of iterated functions Shanghai46 9 11,482 04/21/2023, 09:07 PM
Last Post: Shanghai46
  Computing sqrt 2 with rational functions. tommy1729 0 2,349 03/31/2023, 11:49 AM
Last Post: tommy1729
  [MSE] iterated sin using Besselfunction 1st kind Gottfried 7 8,908 12/18/2022, 02:06 PM
Last Post: Gottfried
  Iterated function convergence Daniel 1 4,086 12/18/2022, 01:40 AM
Last Post: JmsNxn
  Uniqueness of fractionally iterated functions Daniel 7 11,096 07/05/2022, 01:21 AM
Last Post: JmsNxn
Question Iterated Hyperbolic Sine and Iterated Natural Logarithm Catullus 2 4,861 06/11/2022, 11:58 AM
Last Post: tommy1729
  Generalized Kneser superfunction trick (the iterated limit definition) MphLee 25 43,765 05/26/2021, 11:55 PM
Last Post: MphLee
  iterated derivation Xorter 0 4,362 06/09/2019, 09:43 PM
Last Post: Xorter
  1st iterated derivatives and the tetration of 0 Xorter 0 5,706 05/12/2018, 12:34 PM
Last Post: Xorter



Users browsing this thread: 3 Guest(s)