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Re: Better Root Finder [message #53392 is a reply to message #53390]

Sun, 15 April 2007 13:41

jschwab@gmail.com
Messages: 30
Registered: December 2006

Member

On Apr 15, 12:55 am, "Max Watson" <max...@gmail.com> wrote:
> IDL's fx_root seems very limited; when I want to find the root of say
> x^3 - 8 with the initial guess vector [-1,-100,100], IDL returns a
> complex number: ( -1.00000, 1.73205). Is there a way that
> fx_root can be easily modified so that it can find the right answer
> with a bad initial guess?

I wouldn't say that fx_root is limited from that example; it is
finding (one of) the correct (complex) solutions.

If you are only solving polynomial equations and need to get all the
real solutions, you could try fz_roots, which gives you all of the
solutions to a given polynomial. Then pick off the real solutions, or
whatever your desired "right answer" is.

I wouldn't say that's necessarily the best solution, but it's
certainly one of the easiest.

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[Message index]

		Re: Better Root Finder By: wlandsman@jhu.edu on Sun, 15 April 2007 17:01
		Re: Better Root Finder By: jschwab@gmail.com on Sun, 15 April 2007 13:41
		Re: Better Root Finder By: mmeron on Mon, 16 April 2007 12:17

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