.ringDirxy {BayesX} | R Documentation |
Compute direction of points in a polygon.
Description
This is (private, not exported) R code replacing the call to maptools:::.ringDirxy, which links to C code.
Usage
.ringDirxy(xy)
Arguments
xy |
a two-column matrix with x and y coordinates of at least 3 points which form a polygon |
Value
Returns the integer -1 if the direction is counter-clockwise and 1 if the direction is clockwise.
Note
The function uses vectorization and should not be very much slower than the original.
Author(s)
Daniel Sabanes Bove
Examples
## Not run: ## Create test polygon ordered clockwise.
nPoints <- 200
sequence <- seq(1, 10, length = nPoints)
firstHalf <- sequence[1:(nPoints/2)]
test <- cbind(
"x" = c(sequence, rev(sequence)),
"y" = c(firstHalf, rev(firstHalf), -firstHalf, -rev(firstHalf))
)
plot(test, type="n")
polygon(test)
## Compute direction with this and the original function,
BayesX:::.ringDirxy(test)
## End(Not run)
[Package BayesX version 0.3-3 Index]