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My R workflow is usually such that I have a file open into which I type R commands, and I’d like to execute those commands in a separately opened R shell.
The easiest way of doing this is to say source('the-file.r') inside R. However, this always reloads the whole file which may take considerable time if big amounts of data are processed. It also requires me to specify the filename again.
Ideally, I’d like to source only a specific line (or lines) from the file (I’m working on a terminal where copy&paste doesn’t work).
source doesn’t seem to offer this functionality. Is there another way of achieving this?
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When a file is sourced (by typing either source filename or . filename at the command line), the lines of code in the file are executed as if they were printed at the command line. This is particularly useful with complex prompts, to allow them to be stored in files and called up by sourcing the file they are in.
Description. source causes R to accept its input from the named file or URL or connection or expressions directly. Input is read and parse d from that file until the end of the file is reached, then the parsed expressions are evaluated sequentially in the chosen environment.
In Linux systems, source is a built-in shell command that reads and executes the file content in the current shell. These files usually contain a list of commands delivered to the TCL interpreter to be read and run.
Here's another way with just R:
source2 <- function(file, start, end, ...) {
file.lines <- scan(file, what=character(), skip=start-1, nlines=end-start+1, sep='\n')
file.lines.collapsed <- paste(file.lines, collapse='\n')
source(textConnection(file.lines.collapsed), ...)
}
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