On 19/08/2008, at 10:15 AM, hadley wickham wrote:
On Mon, Aug 18, 2008 at 3:54 PM, Rolf Turner
<[EMAIL PROTECTED]> wrote:
On 19/08/2008, at 1:04 AM, stephen sefick wrote:
The real data are counts of aquatic insects at distinct locations
on a
river continuum on the way down a river, so the when a point
point on
the graph is missing (lost sampling equipment for that month) the
points downstream (toward the right) are valid to show a trend.
Aren't they?
Quite possibly; I wouldn't really know. However it would be less
than
honest to plot the interpolated/inferred points as if they were
genuine
data points. By all means plot the interpolations, but
distinguish them,
e.g. by joining them to their neighbours by dotted lines (where
real points
are joined to each other by solid lines).
x <- sort(runif(10))
y <- runif(10)
plot(x, y, type="l")
Doesn't a line plot inherently display a set of linear interpolations?
Yes. And your point is?
Compare:
x <- 1:10
y <- rep(1:2,5)
y[5] <- NA
y0 <- approx(x,y,xout=1:10)
plot(y0,type="l")
with
foo(x,y)
where
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))
}
There is a difference in what you are telling the reader/viewer.
cheers,
Rolf Turner
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