[R] Question regarding R plot
Charles C. Berry
cberry at tajo.ucsd.edu
Sat Apr 17 18:45:59 CEST 2010
On Sat, 17 Apr 2010, Akito Y. Kawahara wrote:
> Hi, I am new to R, and have a quick question regarding an R script
> that I received from a kind colleague.
>
> I am trying to determine the "peak" (maximum value) of the graph that
> is plotted when executing the following. There is an input file called
> "rates_values.txt" which begins as:
>
> rateValue
> 0.375693
> 0
> 1.71274
> 0
> 0
> 1.02832
> 0
> 0.16343
> 1.02349
> 0
> 0
> 1.47258
> 0.703522
> 0.390541
> 1.83415
>
>
>
> The script, below, must run with the rates_values.txt in the same dir.
>
> #-------
> rates<-read.table("rates_values.txt",header=T)
> attach(rates)
> scores<-function(x){
> l<-length(rateValue)
> total<-0
> for(i in 1:l){
> value<-16*rateValue[i]*rateValue[i]*x*exp(-4*rateValue[i]*x)
> total<-total+value
> }
> return(total)
> }
>
>
> #-------
> #preparing the plot
> linewidth=3
> linetype=3
> color="blue"
> xvalue=0.5
>
> plot(scores,xvalue,0,type="n",font.axis=2,xlim=c(xvalue,0))
> curve(scores,xvalue,add=TRUE,col=color,lty=linetype,lwd=linewidth,xlim=c(xvalue,0))
>
> #-------
>
> Can anyone help me figure out how to determine the peak (maximum
> "scores") value in the plot that is generated?
Yes. Anyone who knows something called 'the calculus' could help. And they
could point out that the 0's in the data really do not matter.
If the 0's are real data that should influence the result, it seems there
is something wrong with scores() and you might do well to get a consult
from a statistician.
If you are still determined to solve the problem as stated, see
?optimise
Something like
optimise( scores, range(rateValue), maximum=TRUE )
should do it.
HTH,
Chuck
It should be about 11.7
> but I would like to get an exact value. This should be a relatively
> easy question, but I'm new to R, and what I have tried doesn't seem to
> work.
>
> Thanks!
>
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>
Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
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