Making Rcout output appear on the R console immediately

Question

I have coded an MCMC sampler using Rcpp (specifically, RcppArmadillo). I would like my sampler to print periodic status messages to the R console, but the messages appear all at once when the sampler terminates. The output statement is :

Rcout << "Progress => " 
      << double(iterations) / double(maxit) * 100 
      << "%" 
      << std::endl;

Can this code be augmented so that its output appears on the R console immediately?

R version: 2.14.1

platform: Darwin 9.8.0

Rcpp version: 0.9.10

You might need to flush the console output buffer. In c++ that's std::flush, perhaps there is an Rcpp equivalent? — Thomas, Nov 11 '12 at 01:29

score 2 · Answer 1 · edited May 23 '17 at 11:44

2

This behaviour has been implemented in Rcpp 0.10.0 (to be released soon) following advice from answers to this question.

In the meantime, you can manually call R_FlushConsole

edited May 23 '17 at 11:44

Community

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answered Nov 11 '12 at 11:32

Romain Francois

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While I was there. I implemented `Rcerr` – Romain Francois Nov 11 '12 at 13:27
Neither std::flush nor R_FlushConsole fixes the problem. Outputting is still delayed until the function terminates. – user1815351 Nov 11 '12 at 15:38
thanks for the report. how do you run R ? On OSX's console ? with the standard R app ? – Romain Francois Nov 11 '12 at 15:52
I use the standard app (R GUI version 1.43). – user1815351 Nov 11 '12 at 16:10
In R-devel's code, I can read: `This should have been fixed a long time ago .... Finally in Sep 2012 R.app sets ptr_R_FlushConsole` . Perhaps this works with R-devel. – Romain Francois Nov 12 '12 at 10:40
I upgraded to the latest version of R, but the problem remains. – user1815351 Nov 12 '12 at 16:10
Hmmm. Not sure this has been fixed on R 2.15.2 or in R-devel (2.16.0 to be). Which one did you install ? R-devel is available from here: http://r.research.att.com/ – Romain Francois Nov 12 '12 at 16:16

score 0 · Answer 2 · answered Feb 02 '14 at 11:17

0

flush() and flush.console() are still broken. R 3.0.2 / OSX

answered Feb 02 '14 at 11:17

Allen Day

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score 0 · Answer 3 · edited May 23 '17 at 11:51

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You need a hat trick:

R_FlushConsole();
R_ProcessEvents();
R_CheckUserInterrupt();

Copied from: parallel-computing-in-r-with-c-within-r-functions

edited May 23 '17 at 11:51

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answered Jul 29 '16 at 16:52

Matt Chambers

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Making Rcout output appear on the R console immediately

3 Answers3