Message-ID: <971536df0712061440u18614138wcfde3768c4c58c9@mail.gmail.com>
Date: 2007-12-06T22:40:04Z
From: Gabor Grothendieck
Subject: simple problems
In-Reply-To: <14200401.post@talk.nabble.com>
On Dec 6, 2007 3:26 PM, marciarr <marcia.rocha at gmail.com> wrote:
>
> Hello R users,
> I have been looking through Help files and Nabble list for the answers for
> these simple questions, but it seems to be fruitless.
> 1- in a data frame with two columns, x and y, how do I get the corresponding
> value of x to, let's say, the minimum value of the y column (min (data$y)) ?
In the builtin Formaldehyde data frame find the value of carb (first column)
which corresponds to the least value of optden (second column):
with(Formaldehyde, carb[which.min(optden)])
> 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)