Re: Plotting
- To: mathgroup at smc.vnet.net
- Subject: [mg73000] Re: Plotting
- From: Peter Pein <petsie at dordos.net>
- Date: Sun, 28 Jan 2007 01:07:54 -0500 (EST)
- References: <epfa83$doc$1@smc.vnet.net>
Rayne schrieb:
> Hi all,
> I want to plot the cubic equation f(x) == x^3 - 16x^2 + 3x + 1 == 0. I had:
>
> f==x^3-16 x^2+3 x+1 ==== 0
> Plot[f,{x,-1,20}]
>
> but I was unable to get the plot. The error message says
>
> Plot::plnr: f is not a machine-size real number at x == -0.999999.
> Plot::plnr: f is not a machine-size real number at x == -0.148093.
> Plot::plnr: f is not a machine-size real number at x == 0.780985.
> General::stop: Further output of Plot::plnr
> will be suppressed during this calculation.
>
> How do I get around this problem?
>
> Thank you.
>
> Regards,
> Rayne
>
Hi Rayne,
read about basic syntax issues in the help browser.
Didn't you realize the syntax error "f==x^3...===0 can not be followed by =0"?
My crystall ball fails terribly.
if you want f to be the root(s) of a polynomial, the value(s) will be
constants. And if you want to plot the values of a polynomial, what does the
"====0" mean. What do 4 "="s mean at all and why do you ask Mathematica if f
is equal to x^3-16x^2+3x+1====0? Where has f been defined? Why don't you care
about syntax errors?
I really do not understand what you want, sorry.
Peter
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