Thank you for your response! 'write.table' writes up to 15 decimal digits which is not the machine (double) precision but not far from that - sorry for the misleading comments!
After all I found a way to do what I needed without using disk or much memory and doing only twice as much work as I could with unlimited memory, so I will stick to this approach. --- Prof Brian Ripley <[EMAIL PROTECTED]> wrote: > On Mon, 17 Dec 2007, Moshe Olshansky wrote: > > > Dear List, > > > > Following the below question I have a question of > my > > own: > > Suppose that I have large matrices which are > produced > > sequentially and must be used sequentially in the > > reverse order. I do not have enough memory to > store > > them and so I would like to write them to disk and > > then read them. This raises two questions: > > 1) what is the fastest (and the most economic > > space-wise) way to do this? > > Using save/load is the simplest. Don't worry about > finding better > solutions until you know those are not good enough. > (serialize / > unserialize is another interface to the same > underlying idea.) > > > 2) functions like write, write.table, etc. write > the > > data the way it is printed and this may result in > a > > loss of accuracy. Is there any way to prevent > this, > > except for setting the "digits" option to a higher > > value or using format prior to writing the data? > > Do please read the help before making false claims. > ?write.table says > > Real and complex numbers are written to the > maximal possible > precision. > > OTOH, ?write says it is a wrapper for cat, whose > help says > > 'cat' converts numeric/complex elements in the > same way as 'print' > (and not in the same way as 'as.character' > which is used by the S > equivalent), so 'options' '"digits"' and > '"scipen"' are relevant. > However, it uses the minimum field width > necessary for each > element, rather than the same field width for > all elements. > > so this hints as.character() might be a useful > preprocessor. > > > Is it possible to write binary files (similar to > Fortran)? > > See ?writeBin. save/load by default write binary > files, but use of > writeBin can be faster (and less flexible). > > > Any suggestion will be greatly appreciated. > > Somehow you have missed a great deal of information > about R I/O. > Try help.start() and reading the sections the search > engine shows you > that look relevant. > > > -- > Brian D. Ripley, > [EMAIL PROTECTED] > 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 > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.