Path: news.mathworks.com!not-for-mail
From: "Steven Lord" <slord@mathworks.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: syms and vpa problem
Date: Tue, 7 Aug 2007 21:48:34 -0400
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"P" <prashanthramu@gmail.com> wrote in message 
news:1186516859.503046.118710@22g2000hsm.googlegroups.com...
> Hi all,
>
> I have a variable called
>
> sym_dPhi =
> -282270057375923/2361183241434822606848*cos(phis
> +2835403426559781/1125899906842624)-5849622991223293/18889465931478580854784*cos(phis
> +1649123417284613/281474976710656)+8867307977828847/75557863725914323419136*cos(phis
> +1667188769632673/281474976710656)-6776253911855553/18889465931478580854784*cos(phis
> +5867111522062989/9007199254740992)+7154406299740559/75557863725914323419136*cos(phis
> +6355945788037667/1125899906842624)
>
> where phis is created as syms phis.
>
> vpa(sym_dyPhi,5) yields me
> ans =
>
> [ empty sym ]
>
> Why ?

Do you have a typo in your command or in your posting?  In the first output, 
your variable is named sym_dPhi, while in your command it's sym_dyPhi.  If 
you had a variable named sym_dyPhi that was empty, VPA would return an empty 
sym.  Alternately, if the line in this posting has a typo and you're 
actually computing vpa(sy_dPhi, 5), what is phis at the time you call VPA?

-- 
Steve Lord
slord@mathworks.com