| sourceTo {R.utils} | R Documentation |
Parses and evaluates code from a file or a connection.
This has the same effect as if source(..., local=TRUE) would have
been called from within the given environment.
This is useful when setting up a new local working environment.
## Default S3 method: sourceTo(file, chdir=FALSE, ..., local=TRUE, envir=parent.frame(), modifiedOnly=FALSE)
file |
A connection or a character string giving the pathname
of the file or URL to read from. |
chdir |
If TRUE and file is a pathname, the R
working directory is temporarily changed to the directory
containing file for evaluating. |
... |
Arguments to source(). If argument file is
not explicitly given, the first argument is assumed to be the
file argument. This argument is converted into a string by
as.character().
|
local |
If FALSE, evaluation is done in the global environment,
otherwise in the calling environment. |
envir |
An environment in which source() should be
called. If NULL, the global environment is used. |
modifiedOnly |
If TRUE, the file is sourced only if modified
since the last time it was sourced, otherwise regardless. |
Return the result of source().
This methods recognizes the hook sourceTo/onPreprocess, which
is called after the lines in file has been read, but before they have
been parsed by the R parser, cf. parse().
An onPreprocess hook function should take a character vector
of code lines and return a character vector of code lines.
This can for instance be used to pre-process R source code with special
directives such as VComments.
Note that only one hook function can be used for this function, otherwise an error is generated.
Henrik Bengtsson (http://www.braju.com/R/)
sourceDirectory().
sys.source() and source().
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# Example 1
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cat("=== Example 1 ================================================\n")
foo <- function(file, ...) {
cat("Local objects before calling sourceTo():\n")
print(ls())
res <- sourceTo(file, ...)
cat("Local objects after calling sourceTo():\n")
print(ls())
}
cat("Global objects before calling foo():\n")
lsBefore <- NA
lsBefore <- ls()
foo(file=textConnection(c('a <- 1', 'b <- 2')))
cat("Global objects after calling foo():\n")
stopifnot(length(setdiff(ls(), lsBefore)) == 0)
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# Example 2 - with VComments preprocessor
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cat("=== Example 2 ================================================\n")
preprocessor <- function(lines, ...) {
cat("-----------------------------------------\n")
cat("Source code before preprocessing:\n")
displayCode(code=lines, pager="console")
cat("-----------------------------------------\n")
cat("Source code after preprocessing:\n")
lines <- VComments$compile(lines)
displayCode(code=lines, pager="console")
cat("-----------------------------------------\n")
lines
}
oldHooks <- getHook("sourceTo/onPreprocess")
setHook("sourceTo/onPreprocess", preprocessor, action="replace")
code <- c(
'x <- 2',
'#V1# threshold=-1',
'#Vc# A v-comment log message',
'print("Hello world")'
)
fh <- textConnection(code)
sourceTo(fh)
setHook("sourceTo/onPreprocess", oldHooks, action="replace")