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Re: normalized ALF (Assotiated Legendre Function)

From: Ben Abbott
Subject: Re: normalized ALF (Assotiated Legendre Function)
Date: Tue, 12 Feb 2008 20:42:35 -0500

I've added a check for underflow. This is my first time doing such, so I may be quite off on what is commonly accepted as proper.

The method I used detects an underflow for orders greater than 151.

        octave:104> result_octave1 = legendre  (152, [-1:0.1:1]);
        warning: legendre: results may be  unstable for high orders.

I've attached the script.


Attachment: legendre.m
Description: Binary data

On Feb 12, 2008, at 1:38 PM, Ben Abbott wrote:

On Tuesday, February 12, 2008, at 10:02AM, "Marco Caliari" <address@hidden > wrote:

The normalized Lagrange functions should (almost) never give NaNs of Infs.
The enclosed script fixes a problem in the previous:

octave:1> legendreold(151,-0.9,"norm")(end-1:end)
ans =

octave:2> legendre(151,-0.9,"norm")(end-1:end)
ans =



I've tried to combine the various implementations. I still need to look into adding a warning in then event of an overflow.

We should also add more tests to include the current improvements.


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