[R] how to connect dots by passing NA

[Rolf Turner]

On 17/04/2008, at 12:56 PM, DinoDragon wrote:

> This maybe a silly question. I'm trying to figure out a way to draw  
> a line from a data set which contain NA. Say, I have a set of data as:
>
> x <- c(1.1 2.2 NA 4.4 5.5)  ; y <- c(1:5) # as x,y of point a, b,  
> c, d, and e.
>
> I would like to plot this to a line by using dot-line to connect  
> the two
> adjacent points before and after the NA, something like: (a)______ 
> (b)......(d)______(e)

How's this?

foo <- function(x,y,...) {
plot(x,y,type="n",...)
na <- apply(cbind(x,y),1,function(x){any(is.na(x))})
f <- c(na[-1],FALSE)
x <- x[!na]
y <- y[!na]
f <- f[!na]
n <- length(x)
f <- f[-n]
segments(x[-n],y[-n],x[-1],y[-1],lty=ifelse(f,3,1))
}

set.seed(42)
x <- sort(runif(20))
y <- rnorm(20)
ix <- sample(1:20,3)
iy <- sample(1:20,3)
x[ix] <- NA
y[iy] <- NA
foo(x,y)

	cheers,

		Rolf Turner



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