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From: Jennifer Young on 16 Jun 2010 13:13
Gang-Gyoo JIN and Torsten,

Thank you both so much for taking the time to help me with this. I got the graph I was hoping for! No more error beeps! :)

Best,
Jenn

Torsten Hennig <Torsten.Hennig(a)umsicht.fhg.de> wrote in message <1330048845.353939.1276689577309.JavaMail.root(a)gallium.mathforum.org>...
> > > Hi all,
> > >
> > > I know this is a simple question, but I am not
> > > well-versed in MATLAB and just need to solve a
> > > (complicated) equation and then plot it. The
> > equation
> > > is:
> > >
> > >
> > 44.0526*exp(-2*k*t)=-(log(1-(A/(B*Qm-C)))+A/(B*Qm-C)+X
> >
> > > *(A/(B*Qm-C))^2)/((A/(B*Qm-C))^(1/3)-(A/(B*Qm-C)))
> > >
> > > where A, B, C, k and X are all constants for which
> > I
> > > have values.
> > >
> > > I just need to solve for Qm over a given range of
> > t,
> > > but am not sure how to approach this because I
> > keep
> > > receiving error messages about syms or ezplot
> > issues
> > > for various methods I have attempted. Any help
> > would
> > > be extremely appreciated! Thanks so much. :)
> > >
> > > Jenn
> >
> > Hi Jennifer,
> >
> > I doubt that you can get a symbolic solution for Qm
> > in terms of the other parameters involved.
> > So you will have to use a numerical method.
> >
> > Write your equation as
> > 44.0526*exp(-2*k*t)-(-(log(1-(A/(B*Qm-C)))+A/(B*Qm-C)+
> > X
> > *(A/(B*Qm-C))^2)/((A/(B*Qm-C))^(1/3)-(A/(B*Qm-C))))=0
> > and use fzero or fsolve to solve for the unknown Qm
> > given a value for t.
> >
> > Best wishes
> > Torsten.
>
> Or go the reverse way:
> Insert values for Qm and solve for t (this can be
> done easily in an explicit way).
> Afterwards, for the graphics, reverse the roles
> of Qm and t.
>
> Best wishes
> Torsten.
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