[R] simple problems
Gabor Grothendieck
ggrothendieck at gmail.com
Fri Dec 7 00:42:06 CET 2007
On Dec 6, 2007 6:13 PM, Emmanuel Charpentier <charpent at bacbuc.dyndns.org> wrote:
> Gabor Grothendieck a écrit :
> > On Dec 6, 2007 3:26 PM, marciarr <marcia.rocha at gmail.com> wrote:
>
> [ Snip.... ]
>
> >> 2- how do I solve a simple equation? Considering the equation y= exp(-x)^12,
> >> I would like to find the values of x for, for example, y=0.01, so
> >> exp(-x)^12=0.01. How do I do that using R?
> >> I know those a probably very, very simple questions, but for which I do not
> >> seem to find the answer.
> >
> > Search between 0 and 1 for the root of the indicated function:
> >
> > uniroot(function(x) 0.1 - exp(-x)^12, 0:1)
>
> I beg your pardon ?
>
> I'd rather use high-school algebra/analysis :
> log(exp(-x)^12)=log(0.01)
> 12log(exp(-x)=log(0.01)
> -12x=log(0.01)
> x=-log(0.01)/12=log(100)/12
>
> Rushing for a sophisticated numerical tool without thinking for an
> explicit solution is easy, fast, lazy (I do that every day ...), but
> deprives you of the process of understanding the problem.
>
The posting instructions ask for minimal code and its likely that the
poster did not literally mean that that was the eventual problem.
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