Write values to a file
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 start) and the values written must represent 1 or more entire rows. Begin by opening a file with writeStart, then write values to it in chunks. When writing is done close the file with writeStop.
If you want to write all values of a Raster* object at once, you can also use 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 blockSize can be used to suggest a chunk size to use.
## S4 method for signature 'RasterLayer,character' writeStart(x, filename, options=NULL, format, prj=FALSE, ...) ## S4 method for signature 'RasterBrick,character' writeStart(x, filename, options=NULL, format, prj=FALSE, ...) ## S4 method for signature 'RasterLayer,vector' writeValues(x, v, start, ...) ## S4 method for signature 'RasterBrick,matrix' writeValues(x, v, start, ...) ## S4 method for signature 'RasterLayer' writeStop(x) ## S4 method for signature 'RasterBrick' writeStop(x)
x |
Raster* object |
filename |
character. Output file name |
options |
character, see |
format |
character, see |
prj |
logical. If |
... |
additional arguments as for |
v |
vector (RasterLayer) or matrix (RasterBrick) of values |
start |
Integer. Row number (counting starts at 1) from where to start writing |
RasterLayer or RasterBrick
## Not run:
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)
if(require(rgdal)){
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)
## End(Not run)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.