The best way to get help is to provide a *reproducible* report -- not just
the output, but also the *exact input* that generates it. Mentioning that
something is the "kind of output...I get sometimes" and " I am trying to
fit this...using lsquares" (without specifying how you are calling
lsquares) requires us to guess what you're doing, which isn't a very
reliable way to diagnose issues.
Please reproduce the problem in a *fresh* Maxima (to be sure that there
isn't some previous input that changes the results) and report the inputs.
Thanks,
-s
On Thu, Nov 10, 2011 at 10:07, cheater cheater <cheater00 at gmail.com> wrote:
> Hey, sorry, no - you're right - I just made up that number on the fly,
> because I didn't have the actual output handy.
>
> This is the kind of output with the arbitrary values that I get sometimes:
>
> ["c_c", (8.643714722839287e-6*(2313820*%r18^2*%e^(20*%r19)-1416)
> -20*%r18^2*%e^(20*%r19)+0.0122395) ^2,
> [.001111111111111111*(1000*%r18^2*%e^(1000*%r19)-100*%r18^2*%e^(100*%r19)),
> ((450000*%r18^2*%r19^2-1000*%r18^2*%r19+%r18^2)*%e^(1000*%r19)
> +(45000*%r18^2*%r19^2+100*%r18^2*%r19-%r18^2)*%e^(100*%r19))
> /%r19^2], "\"[[a = %r18,b = %r19,c =
> -8.643714722839287e-6*(2313820*%r18^2*%e^(20*%r19)-1416)]]\""]
>
> Here I am trying to fit this:
>
> y = a^2 * x * exp(b * x) + c
> using lsquares, with the parameters being guessed indicated as [a, b, c].
>
> In this case, you can see the parameter array guessed by lsquares:
> [[a = %r18,b = %r19,c =
> -8.643714722839287e-6*(2313820*%r18^2*%e^(20*%r19)-1416)]]
>
> and also the error calculated by lsquares for that specific fit:
>
> (8.643714722839287e-6*(2313820*%r18^2*%e^(20*%r19)-1416)
> -20*%r18^2*%e^(20*%r19)+0.0122395) ^2
>
> and then an integral counted using the fit: it's basically the area
> between the function's graph - let's say f(x), between x=100, x=1000,
> and a straight line which goes from f(100) to f(1000). Also the slope
> of the mentioned straight line is put out. The integral is:
>
> ((450000*%r18^2*%r19^2-1000*%r18^2*%r19+%r18^2)*%e^(1000*%r19)
> +(45000*%r18^2*%r19^2+100*%r18^2*%r19-%r18^2)*%e^(100*%r19))
> /%r19^2
>
> and the slope is:
>
> .001111111111111111*(1000*%r18^2*%e^(1000*%r19)-100*%r18^2*%e^(100*%r19))
>
> Does this help any further?
>
> I get this sort of error from many fits that I run; I'm not sure where
> to go with this.
>
>
> On Thu, Nov 10, 2011 at 15:35, Richard Fateman
> <fateman at eecs.berkeley.edu> wrote:
> > On 11/10/2011 6:22 AM, cheater cheater wrote:
> >>
> >> Hi again, I have noticed that a lot of people post this info
> >
> > ...
> >
> > It would probably be more useful if you indicated what program you were
> > running.
> > In particular, if your output truly includes 3^2, rather than 9,
> perhaps
> > you have turned
> > off simplification, in which case many programs will not operate
> normally.
> >
> > It could be that using values like 1.0 rather than 1 will help,
> but
> > that is just a guess.
> >
> >
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