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

subarea function