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\name{writeValues}
\alias{writeStart}
\alias{writeStart,RasterLayer,character-method}
\alias{writeStart,RasterBrick,character-method}
\alias{writeStop}
\alias{writeStop,RasterLayer-method}
\alias{writeStop,RasterBrick-method}
\alias{writeValues}
\alias{writeValues,RasterLayer,vector-method}
\alias{writeValues,RasterBrick,matrix-method}
\title{Write values to a file}
\description{
Functions for writing blocks (>= 1 row(s)) of values to files. Writing has to start at the first cell of a row (identified with argument \code{start}) and the values written must represent 1 or more entire rows. Begin by opening a file with \code{writeStart}, then write values to it in chunks. When writing is done close the file with \code{writeStop}.
If you want to write all values of a Raster* object at once, you can also use \code{\link{writeRaster}} which is easier to use but more limited. The functions described here allow writing values to file using chunks of different sizes (e.g. 1 or 10 rows). Function \code{\link{blockSize}} can be used to suggest a chunk size to use.
}
\usage{
\S4method{writeStart}{RasterLayer,character}(x, filename, options=NULL, format, prj=FALSE, ...)
\S4method{writeStart}{RasterBrick,character}(x, filename, options=NULL, format, prj=FALSE, ...)
\S4method{writeValues}{RasterLayer,vector}(x, v, start, ...)
\S4method{writeValues}{RasterBrick,matrix}(x, v, start, ...)
\S4method{writeStop}{RasterLayer}(x)
\S4method{writeStop}{RasterBrick}(x)
}
\arguments{
\item{x}{Raster* object}
\item{filename}{character. Output file name}
\item{options}{character, see \code{\link{writeRaster}}}
\item{format}{character, see \code{\link{writeRaster}}}
\item{prj}{logical. If \code{TRUE}, a "prj" file is written}
\item{...}{additional arguments as for \code{\link{writeRaster}}}
\item{v}{vector (RasterLayer) or matrix (RasterBrick) of values}
\item{start}{Integer. Row number (counting starts at 1) from where to start writing \code{v}}
}
\value{
RasterLayer or RasterBrick
}
\seealso{ \code{\link{writeRaster}, \link{blockSize}, \link{update}} }
\examples{
\dontrun{
r <- raster(system.file("external/test.grd", package="raster"))
# write to a new binary file in chunks
s <- raster(r)
#
tr <- blockSize(r)
tr
s <- writeStart(s, filename='test.grd', overwrite=TRUE)
for (i in 1:tr$n) {
v <- getValuesBlock(r, row=tr$row[i], nrows=tr$nrows[i])
s <- writeValues(s, v, tr$row[i])
}
s <- writeStop(s)
s2 <- writeStart(s, filename='test2.tif', format='GTiff', overwrite=TRUE)
# writing last row first
for (i in tr$n:1) {
v <- getValuesBlock(r, row=tr$row[i], nrows=tr$nrows[i])
s2 <- writeValues(s2, v, tr$row[i])
}
# row number 5 once more
v <- getValuesBlock(r, row=5, nrows=1)
writeValues(s2, v, 5)
s2 <- writeStop(s2)
## write values of a RasterStack to a RasterBrick
s <- stack(system.file("external/rlogo.grd", package="raster"))
# create empty brick
b <- brick(s, values=FALSE)
b <- writeStart(b, filename="test.grd", format="raster",overwrite=TRUE)
tr <- blockSize(b)
for (i in 1:tr$n) {
v <- getValuesBlock(s, row=tr$row[i], nrows=tr$nrows[i])
b <- writeValues(b, v, tr$row[i])
}
b <- writeStop(b)
# note that the above is equivalent to
# b <- writeRaster(s, filename="test.grd", format="raster",overwrite=TRUE)
}
}
\keyword{ spatial }
\keyword{ methods }
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