Most clever! I'd completely forgotten about panel.segments.
Paul Murrell wrote:
>Here's one way to vectorize the lines ...
>
>my.panel2 <- function(x, y, cex=1, ...){
> panel.xyplot(x, y, cex = cex, ...)
> a <- 0.5 * cex *
> convertWidth(unit(1, "char"), "native", valueOnly=TRUE)
> b <- 0.5 * cex *
> convertHeight(unit(1, "char"), "native",valueOnly=TRUE)
> dx <- diff(x)
> dy <- diff(y)
> f <- 1 / sqrt((dx/a)^2 + (dy/b)^2)
> n <- length(x)
> x1 <- x[1:(n-1)] + f*dx
> x2 <- x[2:n] - f*dx
> y1 <- y[1:(n-1)] + f*dy
> y2 <- y[2:n] - f*dy
> i <- f < 0.5
> panel.segments(x1[i], y1[i], x2[i], y2[i])
>}
>
>Paul
>
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