similar to: Low level subsetting and S3 subsetting

On 09/05/2018 11:18 AM, I?aki Ucar wrote: > The bottomline here is that one can always call a base method, > inexpensively and without modifying the object, in, let's say, > *formal* OOP languages. In R, this is not possible in general. It > would be possible if there was always a foo.default, but primitives > use internal dispatch. > > I was wondering whether it would be

I'm looking for a way to get the length of an object 'x' as given by base data type without dispatching on class. Something analogous to how .subset()/.subset2(), e.g. a .length() function. I know that I can do length(unclass(x)), but that will trigger the creation of a new object unclass(x) which I want to avoid because 'x' might be very large. Here's a dummy example

On 08/24/2018 07:55 PM, Henrik Bengtsson wrote: > Is there a low-level function that returns the length of an object 'x' > - the length that for instance .subset(x) and .subset2(x) see? An > obvious candidate would be to use: > > .length <- function(x) length(unclass(x)) > > However, I'm concerned that calling unclass(x) may trigger an > expensive copy

The solution below introduces a dependency on data.table, but otherwise it does what you need: --- # special method for Foo objects length.Foo <- function(x) { length(unlist(x, recursive = TRUE, use.names = FALSE)) } # an instance of a Foo object x <- structure(list(a = 1, b = list(b1 = 1, b2 = 2)), class = "Foo") # its length stopifnot(length(x) == 3L) # get its length as

Hi Tomas, On 09/03/2018 11:49 AM, Tomas Kalibera wrote: > Please don't do this to get the underlying vector length (or to achieve > anything else). Setting/deleting attributes of an R object without > checking the reference count violates R semantics, which in turn can > have unpredictable results on R programs (essentially undebuggable > segfaults now or more likely later

Dear all, I have searched the forums for an answer - and there is plenty of questions along the same line - but none of the paproaches shown worked to my problem: I have a data frame that I get from a csv: summarystats<-as.data.frame(read.csv(file=f_summary)); where I have the columns Dataset, Class, Type, Category,.. Problem1: I want to find a subset of this frame, based on values in

Is there a low-level function that returns the length of an object 'x' - the length that for instance .subset(x) and .subset2(x) see? An obvious candidate would be to use: .length <- function(x) length(unclass(x)) However, I'm concerned that calling unclass(x) may trigger an expensive copy internally in some cases. Is that concern unfounded? Thxs, Henrik

Please don't do this to get the underlying vector length (or to achieve anything else). Setting/deleting attributes of an R object without checking the reference count violates R semantics, which in turn can have unpredictable results on R programs (essentially undebuggable segfaults now or more likely later when new optimizations or features are added to the language). Setting attributes

The bottomline here is that one can always call a base method, inexpensively and without modifying the object, in, let's say, *formal* OOP languages. In R, this is not possible in general. It would be possible if there was always a foo.default, but primitives use internal dispatch. I was wondering whether it would be possible to provide a super(x, n) function which simply causes the

Hi all --- this is less a specific question and more general regarding S3 classes. I've noticed that quite a few very common default implementations of generic functions (e.g. `unique`, `[`, `as.data.frame`) strip away class information. In some cases, it appears conditionals have been created to re-assign the class, but only for a few special types. For example, in `unique.default`, if the

I am a bit confused about the semantics of classes, [, and [[. For at least some important built-in classes (factors and dates), both the getter and the setter methods of [ operate on the class, but though the getter method of [[ operates on the class, the setter method operates on the underlying vector. Is this behavior documented? (I haven't found any documentation of it.) Is it

Hi, I'm wondering why indexing a data frame by row name doesn't work with [[. It works with [: > sw <- swiss[1:5,1:2] > sw["Moutier", "Agriculture"] [1] 36.5 but not with [[: > sw[["Moutier", "Agriculture"]] Error in .subset2(.subset2(x, ..2), ..1) : subscript out of bounds The problem is really with the row name (and not

Hello. I'm currently trying to wrap up data frames into OCaml via OCaml-R, and I'm having trouble with data frame subsetting: > # x#column 1;; > Erreur dans (function(x, i, exact) if (is.matrix(i)) as.matrix(x)[[i]] else .subset2(x, : > l'?l?ment 1 est vide ; > la partie de la liste d'arguments de 'is.matrix' en cours d'?valuation ?tait : > (i)

It looks to me like internally .subset2 uses `get1index()`, but this function is declared in Defn.h, which AFAIK is not part of the exported R API. Looking at the code for `get1index()` it looks like it just loops over the (translated) names, so I guess I just do that [0]. [0]: https://github.com/r-devel/r-svn/blob/1ff1d4197495a6ee1e1d88348a03ff841fd27608/src/main/subscript.c#L226-L235 On Wed,

Hi, Hope you are well. I was wondering if there is a function at C level that is equivalent to mtcars$carb or .subset2(mtcars, "carb"). If I have the index of the column then the answer would be VECTOR_ELT(df, asInteger(idx)) but I was wondering if there is a way to do it directly from the name of the column without having to loop over columns names to find the index? Thank you Best

Hello, my data is contained in nested lists (which seems not necessarily to be the best approach). What I need is a fast way to get subsets from the data. An example: test <- list(list(a = 1, b = 2, c = 3), list(a = 4, b = 5, c = 6), list(a = 7, b = 8, c = 9)) Now I would like to have all values in the named variables "a", that is the vector c(1, 4, 7). The best I could come up

Dear list, can someone explain to me why deparse(substitute(x)) does not seem to work when x is of a user-defined S3 class? In my actual problem, my print method is part of a package, and the method is registered in the NAMESPACE, if that should make a difference. > print.testclass <- function(x,...){ xname <- deparse(substitute(x)) cat("Your object name

Hi, I am running R 2.13.0 on a Windows 7 machine. I ran the script: testInstalledBasic('devel') and received the following warning message: running tests of consistency of as/is.* creating ?isas-tests.R? running code in ?isas-tests.R? comparing ?isas-tests.Rout? to ?isas-tests.Rout.save? ...running tests of random deviate generation -- fails occasionally running code in

Full_Name: Andrew Stryker Version: 1.8.1 OS: Linux/Win XP Submission from: (NULL) (65.124.252.58) >From ?factor: See Also: '[.factor' for subsetting of factors. 'gl' for construction of "balanced" factors and 'C' for factors with specified contrasts. 'levels' and 'nlevels' for accessing the levels, and

Hi all, following sample code illustrates the problem : Date1 <- Date2 <- as.POSIXlt(seq.Date(as.Date("2010-04-01"),as.Date("2011-04-01"),by='day')) identical(Date1,Date2) all.equal(Date1,Date2) identical() gives the correct answer. As there is no all.equal method for POSIXlt objects, all.equal.list is used instead. Subsetting using [[]] doesn't work