writeValues: Write values to a file

In raster: Geographic Data Analysis and Modeling

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 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.

Usage

## 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)

Arguments

x	Raster* object
filename	character. Output file name
options	character, see writeRaster
format	character, see writeRaster
prj	logical. If TRUE, a "prj" file is written
...	additional arguments as for writeRaster
v	vector (RasterLayer) or matrix (RasterBrick) of values
start	Integer. Row number (counting starts at 1) from where to start writing v

Value

RasterLayer or RasterBrick

See Also

writeRaster, blockSize, update

Examples

 

## 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)

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)

raster documentation built on Oct. 3, 2024, 1:08 a.m.