readwrite: Read from, or write to, file

In terra: Spatial Data Analysis

Read from, or write to, file

Description

Methods to read from or write chunks of values to or from a file. These are low level methods for programmers. Use writeRaster if you want to save an entire SpatRaster to file in one step. It is much easier to use.

To write chunks, begin by opening a file with writeStart, then write values to it in chunks using the list that is returned by writeStart. When writing is done, close the file with writeStop.

blocks only returns chunk size information. This can be useful when reading, but not writing, raster data.

Usage

## S4 method for signature 'SpatRaster'
readStart(x)

## S4 method for signature 'SpatRaster'
readStop(x)

## S4 method for signature 'SpatRaster'
readValues(x, row=1, nrows=nrow(x), col=1, ncols=ncol(x), mat=FALSE, dataframe=FALSE, ...)

## S4 method for signature 'SpatRaster,character'
writeStart(x, filename="", overwrite=FALSE, n=4, sources="", ...)

## S4 method for signature 'SpatRaster'
writeStop(x)

## S4 method for signature 'SpatRaster,vector'
writeValues(x, v, start, nrows)

## S4 method for signature 'SpatRaster'
blocks(x, n=4)

fileBlocksize(x)

Arguments

x	SpatRaster
filename	character. Output filename
v	vector with cell values to be written
start	integer. Row number (counting starts at 1) from where to start writing v
row	positive integer. Row number to start from, should be between 1 and nrow(x)
nrows	positive integer. How many rows?
col	positive integer. Column number to start from, should be between 1 and ncol(x)
ncols	positive integer. How many columns? Default is the number of columns left after the start column
mat	logical. If TRUE, values are returned as a numeric matrix instead of as a vector, except when dataframe=TRUE. If any of the layers of x is a factor, the level index is returned, not the label. Use dataframe=TRUE to get the labels
dataframe	logical. If TRUE, values are returned as a data.frame instead of as a vector (also if matrix is TRUE)
overwrite	logical. If TRUE, filename is overwritten
n	positive integer indicating how many copies the data may be in memory at any point in time. This is used to determine how many blocks (large) datasets need to be read
sources	character. Filenames that may not be overwritten because they are used as input to the function. Can be obtained with sources(x)
...	For writeStart: additional arguments for writing files as in writeRaster For readValues: additional arguments for data.frame (and thus only relevant when dataframe=TRUE)

Value

readValues returns a vector, matrix, or data.frame

writeStart returns a list that can be used for processing the file in chunks.

The other methods invisibly return a logical value indicating whether they were successful or not. Their purpose is the side-effect of opening or closing files.

terra documentation built on Oct. 14, 2024, 5:07 p.m.