Selects a Subarea from a Geodata Object
Selects elements of a geodata object wich are within a
rectangular (sub)area
subarea(geodata, xlim, ylim, ...)
geodata |
an object of the class |
xlim |
optional, a vector with selected range of the x-coordinates. |
ylim |
optional, a vector with selected range of the y-coordinates. |
... |
further arguments to be passed to |
The function copies the original geodata object and
selects values of $coords, $data, $borders,
$covariate and $units.m which lies within the selected
sub-area.
Remaining components of the geodata objects are untouched.
If xlim and/or ylim are not provided the function
prompts the user to click 2 points defining an retangle defining the
subarea on a existing plot.
Returns an geodata object, subsetting of the original one provided.
Paulo Justiniano Ribeiro Jr. paulojus@leg.ufpr.br,
Peter J. Diggle p.diggle@lancaster.ac.uk.
foo <- matrix(c(4,6,6,4,2,2,4,4), nc=2)
foo1 <- zoom.coords(foo, 2)
foo1
foo2 <- coords2coords(foo, c(6,10), c(6,10))
foo2
plot(1:10, 1:10, type="n")
polygon(foo)
polygon(foo1, lty=2)
polygon(foo2, lwd=2)
arrows(foo[,1], foo[,2],foo1[,1],foo1[,2], lty=2)
arrows(foo[,1], foo[,2],foo2[,1],foo2[,2])
legend("topleft", c("foo", "foo1 (zoom.coords)", "foo2 (coords2coords)"),
lty=c(1,2,1), lwd=c(1,1,2))
## "zooming" part of The Gambia map
gb <- gambia.borders/1000
gd <- gambia[,1:2]/1000
plot(gb, ty="l", asp=1, xlab="W-E (kilometres)", ylab="N-S (kilometres)")
points(gd, pch=19, cex=0.5)
r1b <- gb[gb[,1] < 420,]
rc1 <- rect.coords(r1b, lty=2)
r1bn <- zoom.coords(r1b, 1.8, xoff=90, yoff=-90)
rc2 <- rect.coords(r1bn, xz=1.05)
segments(rc1[c(1,3),1],rc1[c(1,3),2],rc2[c(1,3),1],rc2[c(1,3),2], lty=3)
lines(r1bn)
r1d <- gd[gd[,1] < 420,]
r1dn <- zoom.coords(r1d, 1.7, xlim.o=range(r1b[,1],na.rm=TRUE), ylim.o=range(r1b[,2], na.rm=TRUE),
xoff=90, yoff=-90)
points(r1dn, pch=19, cex=0.5)
text(450,1340, "Western Region", cex=1.5)
#if(require(geoRglm)){
#data(rongelap)
#points(rongelap)
## zooming the western area
#rongwest <- subarea(rongelap, xlim=c(-6300, -4800))
#points(rongwest)
## now zooming in the same plot
#points(rongelap)
#rongwest.z <- zoom.coords(rongwest, xzoom=3, xoff=2000, yoff=3000)
#points(rongwest.z, add=TRUE)
#rect.coords(rongwest$sub, quiet=TRUE)
#rect.coords(rongwest.z$sub, quiet=TRUE)
#}Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.