R: Read from, or write to, file

read and write {terra} | R Documentation

## 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. When writing is done close the file with `writeStop`.

### 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, ...)

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

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

### 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 matrix instead of as a vector, except when dataframe is `TRUE`
`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` | poistive 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
`...` | additional arguments for writing files as in `writeRaster`

### 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 succesful or not. Their purpose is the side-effect of opening or closing files.

[Package terra version 1.2-5 Index]