similar to: test for end of file on connection

Hi, I am looking for an efficient way of skipping big chunks of lines on a connection (not necessarily at the beginning of the file). One way is to use read lines, e.g. readLines(1e6), but a) this incurs the overhead of construction of the return char vector and b) has a (fairly remote) potential to blow up the memory. Another way would be to use scan(), e.g. scan(con, skip=1e6, nmax=0)

Hi, I thought it would be convenient if the check.names argument to read.table, which currently can only be TRUE/FALSE, could take a function value as well. If the function is supplied it should be used instead of the default make.names. Here is an example where it can come in handy. I tend to keep my data in coma-separated files with a header line. The header line is prefixed with a comment

Hi, Is it possible to modify an object in the parent.env (as opposed to re-bind)? Here is what I tried: > x = 1:3 # try to modify the first element of x from within a new environment > local(get("x", parent.env(environment()))[1] <- NA) Error in eval(expr, envir, enclos) : Target of assignment expands to non-language object # On the other hand retrieval works just fine >

Hi, What is the reason for seq.Date to require the 'by' argument and not to default it to 1 in the example below? > seq(from=as.Date("1996-01-01"), to=as.Date("1996-12-01")) Error in seq.Date(from = as.Date("1996-01-01"), to = as.Date("1996-12-01")) : exactly two of `to', `by' and `length.out' / `along.with' must be specified

Hi, It seems that a formal function argument can not default to an "outer" variable of the same name: > x <- "foo" > ff <- function(x=x) x > ff() Error in ff() : recursive default argument reference > Is this intentional? Why? I use R-1.9.1. Thanks, Vadim

I believe IO in R is slow because of the way it is implemented, not because it has to do some extra work for the user. I compared scan() with 'what' argument set (which is, AFAIK, is the fastest way to read a CSV file) to an equivalent C code. It turned out to be 20 - 50 times slower. I can see at least two main reasons why R's IO is so slow (I didn't profile this though): A) it

Hi, I tried to write the dim method for the list class, but R doesn't seem to dispatch to it: > dim.list = function(x) c(length(x[[1]]), length(x)) > dim(list(1)) NULL > dim.list(list(1)) [1] 1 1 What is the correct way of registering dim.list with .Primitive("dim")? Thanks, Vadim [[alternative HTML version deleted]]

Hi, To speed up reading of large (few million lines) CSV files I am writing custom read functions (in C). By timing various approaches I figured out that one of the bottlenecks in reading character fields is the mkChar() function which on each call incurs a lot of garbage-collection-related overhead. I wonder if there is a "vectorized" version of mkChar, say mkChar2(char **, int

Hi, I am looking for a way to extract an "interesting" part of the match to a regular expression. For example the pattern "[./](*.)" matches a substring that begins with either "." or "/" followed by anything. I am interested in this "anything" w/o the "." or "/" prefix. If say I match the pattern against "abc/foo" I

Hi, I have two data sources. One records time in PST time zone, the other in GMT. I want to compute the difference between the two, but don't see how. Here is an example where I compute time difference between identical times each (meant to be) relative to its time zone. > as.POSIXlt("2000-05-10 10:15:00", "PST") - as.POSIXlt("2000-05-10 10:15:00",

Hi, I am writing C++ functions that are to be called via .Call() interface. I'd been using error() (from R.h) to return to R if there is an error, but then I realized that this might be not safe as supposedly error() doesn't throw an exception and therefore some destructors do not get called and some memory may leak. Here is a simple example extern "C" void foo() { string

Hi, Don't know if it belongs to r-devel or r-help, but since I am planning to alter some of R's internal code I am sending it here. The existing implementation of the sample() function, when the optional 'prob' argument is given, is quite inefficient. The complexity is O(sampleSize * universeSize), see ProbSampleReplace() and ProbSampleNoReplace() in random.c. This makes the

Hi, Is it possible to redirect the staff that normally goes to the R console window into a file. sink() does this for sdterr and stdout. But I need something that redirects "everything" that appear in the console window (including the top-level commands). I want to achieve the same effect as that of the following command under sh: R < foo.R &> foo.Rt only I want the

Hi, As far as I can tell data.frame class adds two features to those of lists: * matrix structure via [,] and [,]<- operators (well, I know these are actually "["(i, j, ...), not "[,]"). * row names attribute. It seems that the overhead of the support for the row names, both computational and RAM-wise, is rather non-trivial. I frequently subscript from a data.frame,

Hi, It seems like reading a line from a gzfile() connection changes the mode of the connection from text to binary (it also alters "can write", in case it matters). The following transcript, produced on RedHat 7.1, demonstrates this "feature" (note the evolution of file$text). Is this expected? Thanks, Vadim > file <- gzfile("foo.gz") file <-

Hi, I am building R on RH Linux 7.3 and I noticed that ./configure does not set the optimization flag, -O or -O2, for gcc, but does set for g++ and g77. Why is that? Should I try to set it manually, if yes how? Thanks, Vadim P.S. This is the bottom portion of the ./configure run R is now configured for i686-pc-linux-gnu Source directory: . Installation directory:

Thank you for the reference to Knuth. Indeed in vol. 2 he has a > -----Original Message----- > From: Tony Plate [mailto:tplate@blackmesacapital.com] > Sent: Friday, September 24, 2004 8:05 AM > To: Vadim Ogranovich > Subject: Re: [Rd] algorithm reference for sample() > > Have you tried looking in Knuth's books on computer > algorithms? (They are classics for good

Hi, I have an SEXP obj in a C function called via .Call(). The obj is protected (in fact it is an argument to .Call and therefore automatically protected). If I set an attribute of obj does the attribute become protected too? Here is an example SEXP foo(SEXP obj) { SET_NAMES(obj, NEW_CHARACTER(3)); /* are names protected or not? */ ... } Thanks, Vadim [[alternative HTML version

Hi, Encouraged by a tip from Simon Urbanek I tried to use the S3 machinery to write a faster version of the data.frame class. This quickly hits a snag: the "[.default"(x, i) for some reason cares about the dimensionality of x. In the end there is a full transcript of my R session. It includes the motivation for writing the class and the problems I have encountered. As a result I see

Hi, I am building r-patch from the sources (rsync-ed today). make check produced the following message: running tests of Internet and socket functions expect some differences make[3]: Entering directory `/usr/evahome/vograno/R/tests' running code in 'internet.R' ... OK comparing 'internet.Rout' to './internet.Rout.save' ...18c18 < Content type `text/plain;