[R] help

[Sarah Goslee]

Good plan.

Also, please notice that you need to hit "reply all" to send your
messages to the list and not just to me.

Sarah

On Tue, May 15, 2012 at 10:34 AM, Eva-Lotta Blom
<eva-lotta.blom at bioenv.gu.se> wrote:
> yes i should have done that, sorry for this i was just very frustrated and
> could not solve it. I guess i only needed hint for commands and not the
> solution. I will think a bit more and maybe
> i get back too you with a more well formulated question.
> I think this is a very good site and you are doing a fantastic job.
> cheers
> Lotta
>
>
>
>
>
>
> 15 maj 2012 kl. 16:24 skrev Sarah Goslee:
>
> Lotta,
>
> If this isn't homework, then you need to read the posting guide (see
> link at bottom of each posting to the list), and ask a more specific
> question than "can't get any further."
>
> What have you tried? What didn't work? Where did it go wrong? What
> book are you working from? Etc. Even if not an ethics violation, your
> question is too vague to be easily answered unless you can find
> someone interested in working the entire problem from scratch. Since
> we're all busy volunteers, that's unlikely. You need to do the work of
> asking a well-formed question before you can expect much help.
>
> Sarah
>
> On Tue, May 15, 2012 at 10:10 AM, Eva-Lotta Blom
> <eva-lotta.blom at bioenv.gu.se> wrote:
>
> Hello Sarah
>
> this is not a homework, i am trying to understand R by doing some exercise
>
> in my book.
>
> I will however participate a course in R in august and thought it could be
>
> good to have some
>
> knowledge before. I hoped for help from you since i have no instructor to
>
> ask, that would have been
>
> my first choice.
>
> Ill look for help somewhere else then.
>
> thanks anyway
>
> Lotta
>
>
>
>
>
>
>
>
>
>
> 15 maj 2012 kl. 15:58 skrev Sarah Goslee:
>
>
> Hi,
>
>
> R-help is not a homework help list. If you're having trouble, you need
>
> to speak with your instructor instead.
>
>
> Best of luck,
>
> Sarah
>
>
>
> On Tue, May 15, 2012 at 8:04 AM, Eva-Lotta Blom
>
> <eva-lotta.blom at bioenv.gu.se> wrote:
>
>
>
>  1.  Emma is performing an experiment that requires individual handling of
>
> some animals. The sizes of the animals are lognormally distributed: The
>
> natural logarithms of their sizes has a normal distribution with mean 3 and
>
> standard deviation 0.4. The time (in minutes) it takes to handle each animal
>
> is given by
>
>
>
> 10 + s · 1.5 + eε for animals with s ≤ 20 20 + s · 0.8 + eε for animals with
>
> s > 20
>
>
>
> where ε is a random variable that is normally distributed with expectation 1
>
> and variance 0.3.
>
>
>
> For a randomly picked animal, what is the (approximate) probability that it
>
> can be handled in less than 30 minutes?
>
>
>
> We can solve this exercise using simulation, as follows: Simulate a vector S
>
> with the sizes of 10000 animals, by using the rnorm function and the “exp”
>
> function. Then, compute a vector Time of length 10000 with the times it
>
> takes to handle each of these 10000 animals: Remember that to separate
>
> between the two cases, you can use notation like for example “Time[S < 20]”.
>
> The random component eε can be added by combining the “exp” function with
>
> the “rnorm” function. Finally, you can find the proportion of simulated
>
> values below 30. Re-do the computations a couple of times to get an idea of
>
> the variability of the result.
>
>
>
> s <- c(10000)
>
>
> S <- exp(rnorm(s, 3, 0.4)) [1]# vector 10000, mean, sd
>
>
> Time <- 10+S*1.5 [1] # 10 + s · 1.5 + eε for animals with s ≤ 20
>
>
> time <- 20+S*0.8 [1] #   20 + s · 0.8 + eε for animals with s > 20
>
>
>
> can't get any further and i can't really find a good help page to solve the
>
> code.
>
>
> can you help me?
>
>
> Lotta
>
>


-- 
Sarah Goslee
http://www.functionaldiversity.org