source causes R to accept its input from the named file or URL
or connection or expressions directly. Input is read and
parsed from that file
until the end of the file is reached, then the parsed expressions are
evaluated sequentially in the chosen environment.
withAutoprint(exprs) is a wrapper for source(exprs =
exprs, ..) with different defaults. Its main purpose is to evaluate
and auto-print expressions as if in a toplevel context, e.g, as in the
R console.
source(file, local = FALSE, echo = verbose, print.eval = echo,
exprs, spaced = use_file,
verbose = getOption("verbose"),
prompt.echo = getOption("prompt"),
max.deparse.length = 150, width.cutoff = 60L,
deparseCtrl = "showAttributes",
chdir = FALSE,
encoding = getOption("encoding"),
continue.echo = getOption("continue"),
skip.echo = 0, keep.source = getOption("keep.source"))withAutoprint(exprs, evaluated = FALSE, local = parent.frame(),
print. = TRUE, echo = TRUE, max.deparse.length = Inf,
width.cutoff = max(20, getOption("width")),
deparseCtrl = c("keepInteger", "showAttributes", "keepNA"),
…)
a connection or a character string giving the
pathname of the file or URL to read from. "" indicates the
connection stdin().
TRUE, FALSE or an environment, determining
where the parsed expressions are evaluated. FALSE (the
default) corresponds to the user's workspace (the global
environment) and TRUE to the environment from which
source is called.
logical; if TRUE, each expression is printed
after parsing, before evaluation.
logical; if TRUE, the result of
eval(i) is printed for each expression i; defaults
to the value of echo.
for source() and withAutoprint(*, evaluated=TRUE):
instead of specifying file, an
expression, call, or list
of call's, but not an unevaluated “expression”.
for withAutoprint() (with default evaluated=FALSE):
one or more unevaluated “expressions”.
logical indicating that exprs is passed to
source(exprs= *) and hence must be evaluated, i.e., a formal
expression, call or list of calls.
logical indicating if newline (hence empty line) should
be printed before each expression (when echo = TRUE).
if TRUE, more diagnostics (than just
echo = TRUE) are printed during parsing and evaluation of
input, including extra info for each expression.
character; gives the prompt to be used if
echo = TRUE.
integer; is used only if echo is
TRUE and gives the maximal number of characters output for
the deparse of a single expression.
integer, passed to deparse() which
is used (only) when there are no source references.
character vector, passed as
control to deparse(), see also
.deparseOpts. In R version <= 3.3.x, this was
hardcoded to "showAttributes", which is the default
currently; deparseCtrl = "all" may be preferable, when strict
back compatibility is not of importance.
logical; if TRUE and file is a pathname,
the R working directory is temporarily changed to the directory
containing file for evaluating.
character vector. The encoding(s) to be assumed when
file is a character string: see file. A
possible value is "unknown" when the encoding is guessed: see
the ‘Encodings’ section.
character; gives the prompt to use on
continuation lines if echo = TRUE.
integer; how many comment lines at the start of the
file to skip if echo = TRUE.
logical: should the source formatting be retained when echoing expressions, if possible?
(for withAutoprint():) further (non-file related)
arguments to be passed to source(.).
By default the input is read and parsed in the current encoding of the R session. This is usually what it required, but occasionally re-encoding is needed, e.g.if a file from a UTF-8-using system is to be read on Windows (or vice versa).
The rest of this paragraph applies if file is an actual
filename or URL (and not "" nor a connection). If
encoding = "unknown", an attempt is made to guess the encoding:
the result of localeToCharset() is used as a guide. If
encoding has two or more elements, they are tried in turn until
the file/URL can be read without error in the trial encoding. If an
actual encoding is specified (rather than the default or
"unknown") in a Latin-1 or UTF-8 locale then character strings
in the result will be translated to the current encoding and marked as
such (see Encoding).
If file is a connection (including one specified by "",
it is not possible to re-encode the input inside source, and so
the encoding argument is just used to mark character strings in the
parsed input in Latin-1 and UTF-8 locales: see parse.
Note that running code via source differs in a few respects
from entering it at the R command line. Since expressions are not
executed at the top level, auto-printing is not done. So you will
need to include explicit print calls for things you want to be
printed (and remember that this includes plotting by lattice,
FAQ Q7.22). Since the complete file is parsed before any of it is
run, syntax errors result in none of the code being run. If an error
occurs in running a syntactically correct script, anything assigned
into the workspace by code that has been run will be kept (just as
from the command line), but diagnostic information such as
traceback() will contain additional calls to
withVisible.
All versions of R accept input from a connection with end of line marked by LF (as used on Unix), CRLF (as used on DOS/Windows) or CR (as used on classic Mac OS) and map this to newline. The final line can be incomplete, that is missing the final end-of-line marker.
If keep.source is true (the default in interactive use), the
source of functions is kept so they can be listed exactly as input.
Unlike input from a console, lines in the file or on a connection can contain an unlimited number of characters.
When skip.echo > 0, that many comment lines at the start of
the file will not be echoed. This does not affect the execution of
the code at all. If there are executable lines within the first
skip.echo lines, echoing will start with the first of them.
If echo is true and a deparsed expression exceeds
max.deparse.length, that many characters are output followed by
.... [TRUNCATED] .
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
demo which uses source;
eval, parse and scan;
options("keep.source").
sys.source which is a streamlined version to source a
file into an environment.
‘The R Language Definition’ for a discussion of source directives.
someCond <- 7 > 6
## want an if-clause to behave "as top level" wrt auto-printing :
## (all should look "as if on top level", e.g. non-assignments should print:
if(someCond) withAutoprint({
x <- 1:12
x-1
(y <- (x-5)^2)
z <- y
z - 10
})
## If you want to source() a bunch of files, something like
## the following may be useful:
sourceDir <- function(path, trace = TRUE, ...) {
for (nm in list.files(path, pattern = "[.][RrSsQq]$")) {
if(trace) cat(nm,":")
source(file.path(path, nm), ...)
if(trace) cat("\n")
}
}
suppressWarnings( rm(x,y) ) # remove 'x' or 'y' from global env
withAutoprint({ x <- 1:2; cat("x=",x,"\n"); y <- x^2 })
## x and y now exist:
stopifnot(identical(x, 1:2), identical(y, x^2))
withAutoprint({ formals(sourceDir); body(sourceDir) },
max.dep = 20, verbose = TRUE)
<!-- %% --> tests in ../../../../tests/eval-etc.R -->
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