# [R] simple problems

Emmanuel Charpentier charpent at bacbuc.dyndns.org
Fri Dec 7 00:13:23 CET 2007

```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'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.

Which was probably the point of this (probable) homework...

Emmanuel Charpentier

```