[R] plot of Bernoulli data

[Warnes, Gregory R]

In the next release of the gregmisc library there is a function "wapply"
that applies a specified function over 'windows' of x-y data (code below).
You would use it in this case as:

 x<-sort(runif(100,1,20))
 p<-pnorm(x,10,3)
 y<-as.numeric(runif(x)<p)
 plot(x,y)
 lines(x,p)

 # draw a line with 10 points, each computed on regions spanning 1/5th of
the x range
 lines(wapply(x,y,n=10,width=1/5),col="red")

-Greg



# $Id: wapply.R,v 1.2 2001/08/31 23:45:45 warneg Exp $
#
"wapply" _ function( x, y, fun=mean, method="range",
                    width=1/10, n=50, ...)
{
  method <- match.arg(method, c("width","range","nobs","fraction"))

  if(method == "width" || method == "range" )
    {
      if(method=="range")
        width <- width * range(x)
      
      
      pts _ seq(min(x),max(x),length.out=n)
      
      result _ sapply( pts, function(pts,y,width,fun,XX,...)
                      {
                        low _ min((pts-width/2),max(XX))
                        high _ max((pts+width/2), min(XX))
                        return (fun(y[(XX>= low) & (XX<=high)],...))
                      },
                      y=y,
                      width=width,
                      fun=fun,
                      XX = x,
                      ...)
      
      return(x=pts,y=result)
    }
  else # method=="nobs" || method=="fraction"
    {
      if( method=="fraction")
        width <- floor(length(x) * width)
      
      ord <- order(x)
      x  <- x[ord]
      y  <- y[ord]

      n  <- length(x)
      center  <- 1:n
      below <- sapply(center - width/2, function(XX) max(1,XX) )
      above <- sapply(center + width/2, function(XX) min(n,XX) )

      retval  <- list()
      retval$x  <- x
      retval$y  <- apply(cbind(below,above), 1,
                         function(x) fun(y[x[1]:x[2]],...) )
                         
      return(retval)
    }
      
}



 >  -----Original Message-----
 >  From: Bill Simpson [mailto:wsi at gcal.ac.uk]
 >  Sent: Tuesday, October 02, 2001 7:57 AM
 >  To: r-help at stat.math.ethz.ch
 >  Subject: Re: [R] plot of Bernoulli data
 >  
 >  
 >  >  x<-sort(runif(100,1,20))
 >  >  p<-pnorm(x,10,3)
 >  >  y<-as.numeric(runif(x)<p)
 >  >  plot(x,y)
 >  >  lines(x,p)
 >  df<-data.frame(x,y)
 >  aggregate(df,list(x=(x<5),(x>5)&(x<10),(x>10) & 
 >  (x<15),(x>15)), FUN=mean)
 >  gives me what I want but if anyone has a better way to collect the
 >  observations into bins I'd like to hear it. It would be nice to
 >  pass along something like
 >  breaks<-c(5,10,15,20)
 >  
 >  Thanks
 >  
 >  Bill Simpson
 >  
 >  -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.
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