On Dec 6, 2007 6:13 PM, Emmanuel Charpentier <[EMAIL PROTECTED]> wrote: > Gabor Grothendieck a écrit : > > On Dec 6, 2007 3:26 PM, marciarr <[EMAIL PROTECTED]> 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. >
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