[R] some questions

[Liaw, Andy]

From: Ales Ziberna
> 
> Firstly, these are all very basic questions, thah you coukld 
> probobly answer 
> yourself by searching the manual and help files. 
> Nevertheless, here are the 
> answers to give you a little head start.
> 
> > Dear R expert,
> > The following is my questions:
> >
> > 1. How to generate two sequences of 150 uniform
> > deviates, called v1 and v2, in the range [-1,1].
> v1<-runif(n=150,min=-1,max=1)
> v2<-runif(n=150,min=-1,max=1)
> 
> > 2. How to compute  r=(v1)^2+(v2)^2
> r<-(v1)^2+(v2)^2
> 
> > 3.If r is outside the range of (0,1) then it will be
> > discarded.
> newr<-r[r<1]
> newr<-newr[r>0]

I guess you meant

  newr <- newr[newr > 0]

for the second line above?  I would do it in one line as 

  newr <- r[abs(r - 0.5) < 0.5]

Andy

 
> > 4 How to compute (v1)*sqrt(-2*log(r)/r) and output the
> > first 100 z values in the list.
> z<-(v1)*sqrt(-2*log(r)/r)
> z[1:100] #or
> print(z[1:100])
> 
> > 5. Plot histograms for the sequences from steps 1 and
> > 2.
> hist(v1)
> hist(v2)
> hist(r)
> 
> >
> > Thanks very much for your help!
> I hope this helps,
> 
> Ales Ziberna
> 
> >
> > xingyu
> >
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