R help - Nov 2004 - (no subject)

Good afternoon,
I'd like to know how to superimpose a Student distribution pt on a 
histogram.  I think I have to use the plot function but I don,t know the 
details.
Other question: what is a quntile function?
Can you help me?
Thank you.

Angela Re <angelare at to.infn.it> writes:
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
Please do. You have been told before.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907

On 26-Nov-04 Angela Re wrote:
> Good afternoon,
> I'd like to know how to superimpose a Student distribution pt on a 
> histogram.  I think I have to use the plot function but I don,t know
> the details.
  x<-rt(5000,4)               # draw a sample from t with df=4
  hist(x,breaks=0.5*(-40:40)) # draw histogram with bin-width=0.5
  x0<-0.1*(-200,200)          # breakpoints for pt plot
  lines(x0,dt(x0,4)*5000*0.5) # superimpose the pt plot

DON'T use 'plot' for the last one: it will create a new plot,
while 'lines' (like 'points') adds a plot to an existing plot.
> Other question: what is a quntile function?
(?quantile) Given a distribution P(X <= x) for a random
variable X, the quantile of the distribution corresponding
to probability p (or percentage 100*p) is the value x_p
such that P(X <= x_p) = p (when using percentages it is usually
called the percentile).

Ted.


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Date: 26-Nov-04                                       Time: 16:47:29
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