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Re: Plotting symbolic representation of numerica function

Without the functions g1 and g2 and the value x, we're just guessing, but FindRoot is a NUMERICAL solver. Your FindRoot call cannot succeed without values for all three of them.

That is, x can't be an undefined symbol, as your plot statement evidently expects it to be.


On Sat, 19 Feb 2005 02:32:07 -0500 (EST), mbekkali <mbekkali at> wrote:

> Hello.  I need to plot solutions to system of equations solved using
> numerical functions.  I tried:
> {f1[(x_)?NumericQ],f2[(x_)?NumericQ]}:={f1,f2}/.FindRoot[{g1[f1,f2,x]==0,g2[f1,f2,x]==0},{f1,0},{f2,0}][[1]]
> Plot[Evaluate[{f1[x],f2[x]},{x,x0,x1}]
> where g1,g2 are some functions and x0,x1 some starting variables.  I
> get an error message SetDelayed::shape : Lists
> {f1[x_?NumericQ],f2[x_?NumericQ]} and {f1,f2} are not the same shape.
> I suspect that there is something wrong with SetDelayed because using
> Set and Solve plots functions, yet SetDelayed and Solve generates the
> same message as SetDelayed and FindRoot.
> I do not understand what is wrong and help file is not useful as it
> does not contain examples with SetDelayed for several variables.
> Mukhtar Bekkali

DrBob at

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