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st: Mata - polyroots() issue


From   John Bates <lirac271@yahoo.com>
To   Stata <statalist@hsphsun2.harvard.edu>
Subject   st: Mata - polyroots() issue
Date   Wed, 6 May 2009 20:22:43 -0700 (PDT)

Hi,

I am running Stata 10.1 on Mac OS 10.4.  The following issue is perplexing me:

-------
mata:
mata clear
polynomial1 = (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-30,29)
polyeval(polynomial1,1)
polyroots(polynomial1)  
-------

The polyeval line makes it clear that x=1 is a root for this polynomial.  However, 1 is not a reported result for polyroots.  What is odd is that if I add or subtract a zero term to the polynomial, polyroots() will then correctly report x=1 as a root.  i.e., the following works:

-------
mata:
mata clear
polynomial1 = (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-30,29)
polynomial2 = (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-30,29)
polynomial3 = (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-30,29)
polyroots(polynomial2)
polyroots(polynomial3)  
-------

Does anybody know what is going on here?

Lirac



      

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