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: Wed, 8 Aug 2007 10:25:07 -0400
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"P" <prashanthramu@gmail.com> wrote in message 
news:1186548206.565623.216510@k79g2000hse.googlegroups.com...
> On Aug 7, 9:48 pm, "Steven Lord" <slord@mathworks.com> wrote:
>> "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
>
> Hi Steve,
>
> Thanks for replying !
>
> Sorry about my initial post. I guarantee no typos in my script.
>
> when I call "phis", its still a sym ... meaning I have not substituted
> at value. I do that in the next step using subs(sym_dyPhi,some_value).
>
> What next ?

I think you're going to need to post:

the content of the sym_dyPhi variable
the content of the phis variable
the value you're substituting into sym_dyPhi
the output of "subs(sym_dyPhi, <the value you're substituting in>)"

-- 
Steve Lord
slord@mathworks.com