[Rd] Error generated by .Internal(nchar) disappears when debugging

Joris Meys jorismeys at gmail.com
Mon Oct 5 16:22:08 CEST 2015

Hi all,

I have a puzzling problem related to nchar. In R 3.2.1, the internal nchar
gained an extra argument (see

I've been testing code using the package copula, and at home I'm still
running R 3.2.0 (I know, I know...). When trying the following code, I got
an error:

> library(copula)
> fgmCopula(0.8)
Error in substr(sc[i], 2, nchar(sc[i]) - 1) :
  4 arguments passed to .Internal(nchar) which requires 3

So I do the obvious and try to debug using debug():

> debugonce(fgmCopula)
> fgmCopula(0.8)

And when I try that, I can step through the complete function without any
error. I know that the obvious solution is to update to R 3.2.2, but :

- I have absolutely no clue how a function can give an error when used
normally, but not return any error when stepping through it using debug.
- The copula package built for R 3.2.2 isn't compatible any longer with R
versions older than R 3.2.1, like the one used in our PC classes. Other
packages might share the same problem.

Can somebody shed some light on what exactly is going on here? I don't want
to bug the authors of the copula package if I'm not sure of the origin of
this problem.

Joris Meys
Statistical consultant

Ghent University
Faculty of Bioscience Engineering
Department of Mathematical Modelling, Statistics and Bio-Informatics

tel :  +32 (0)9 264 61 79
Joris.Meys at Ugent.be
Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php

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