readAsciiGrid {maptools} | R Documentation |
read/write to/from ESRI asciigrid format
readAsciiGrid(fname, as.image = FALSE, plot.image = FALSE, colname = basename(fname), proj4string = CRS(as.character(NA))) writeAsciiGrid(x, fname, attr = 1, na.value = -9999, ...)
fname |
file name |
as.image |
logical; if FALSE, a list is returned, ready to be
shown with the image command; if FALSE an object of
class SpatialGridDataFrame-class is returned |
plot.image |
logical; if TRUE, an image of the map is plotted |
colname |
alternative name for data column if not file basename |
proj4string |
A CRS object setting the projection arguments of the Spatial Grid returned |
x |
object of class SpatialGridDataFrame |
attr |
attribute column; if missing, the first column is taken; a name or a column number may be given |
na.value |
numeric; value given to missing valued cells in the resulting map |
... |
arguments passed to write.table, which is used to write the numeric data |
readAsciiGrid
returns the grid map read; either as
an object of class SpatialGridDataFrame-class or, if
as.image is TRUE, as list with components x
, y
and {z}.
Edzer J. Pebesma, e.pebesma@geo.uu.nl
as.image.SpatialGridDataFrame, image
x <- readAsciiGrid(system.file("grids/test.ag", package="maptools")[1]) summary(x) image(x) xp <- as(x, "SpatialPixelsDataFrame") abline(h=332000, lwd=3) xpS <- xp[coordinates(xp)[,2] < 332000,] summary(xpS) xS <- as(xpS, "SpatialGridDataFrame") summary(xS) tmpfl <- paste(tempdir(), "testS.ag", sep="/") writeAsciiGrid(xS, tmpfl) axS <- readAsciiGrid(tmpfl) opar <- par(mfrow=c(1,2)) image(xS, main="before export") image(axS, main="after import") par(opar) unlink(tmpfl)