contextstack overflow

I?m an absolute beginner in R programming?I have a really long R-code with
many variables. When I run the program I always get an error at the same
place called ?contextstack overflow?. Does anybody know what to do in this
case? Are there so strict limitations in R? If yes, is it possible to handle
it? How?

There are limits, and they are quite high -- it is far more likely that 
you have an error in your R code.

In this particular case, it is saying that you have more than 50 nested 
parse contexts -- that is nested if, [, [[, {, ( calls.

I find it helpful to use a syntax-aware editor (e.g. ESS) as that will 
highlight these things for you via indentation patterns.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595