[R] Which language is faster for numerical computation?

[Prof. John C Nash]

Dirk E. has properly focussed the discussion on measurement rather than opinion. I'll add 
the issue of the human time taken to convert, and more importantly debug, interfaced code. 
That too could be measured, but we rarely see human hours to code/debug/test reported.

Moreover, I'll mention the cat among the pigeons of Rcgmin, which I wrote to allow me to 
play with an optimization code more easily to discover where the algorithm might be 
improved. The resulting package on some problems outperforms C equivalents. Now the code 
is quite vectorized, but this has still been a very nice surprise. In fact, I've decided 
to avoid playing around with the interfaces if I can run things well-enough entirely in R.

JN