Evaluate an R expression and captures the output
Evaluate an R expression and captures the output.
captureOutput(expr, file=NULL, append=FALSE, collapse=NULL, envir=parent.frame())
expr |
The R expression to be evaluated. |
file |
A file name or a |
append |
If |
collapse |
A |
envir |
The |
This method imitates capture.output with the major
difference that it captures strings via a raw connection rather
than via internal strings. The latter becomes exponentially slow
for large outputs [1,2].
Henrik Bengtsson
[1] R-devel thread 'capture.output(): Using a rawConnection() [linear] instead of textConnection() [exponential]?', 2014-02-04. https://stat.ethz.ch/pipermail/r-devel/2014-February/068349.html [2] JottR blog post 'PERFORMANCE: captureOutput() is much faster than capture.output()', 2015-05-26. https://www.jottr.org/2014/05/26/captureoutput/
Internally, eval() is used to evaluate the expression.
and capture.output to capture the output.
# captureOutput() is much faster than capture.output()
# for large outputs when capturing to a string.
for (n in c(10e3, 20e3, 30e3, 40e3)) {
printf("n=%d\n", n)
x <- rnorm(n)
t0 <- system.time({
bfr0 <- capture.output(print(x))
})
print(t0)
t1 <- system.time({
bfr <- captureOutput(print(x))
})
print(t1)
print(t1/t0)
bfr2n <- captureOutput(print(x), collapse="\n")
bfr2r <- captureOutput(print(x), collapse="\r")
stopifnot(identical(bfr, bfr0))
} # for (n ...)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.