Martin Maechler
2022-Feb-03 11:14 UTC
[Rd] model.weights and model.offset: request for adjustment
>>>>> Ben Bolker >>>>> on Tue, 1 Feb 2022 21:21:46 -0500 writes:> The model.weights() and model.offset() functions from the 'stats' > package index possibly-missing elements of a data frame via $, e.g. > x$"(offset)" > x$"(weights)" > This returns NULL without comment when x is a data frame: > x <- data.frame(a=1) > x$"(offset)" ## NULL > x$"(weights)" ## NULL > However, when x is a tibble we get a warning as well: > x <- tibble::as_tibble(x) > x$"(offset)" > ## NULL > ## Warning message: > ## Unknown or uninitialised column: `(offset)`. > I know it's not R-core's responsibility to manage forward > compatibility with tibbles, but in this case [[-indexing would seem to > be better practice in any case. Yes, I would agree: we should use [[ instead of $ here in order to force exact matching just as principle Importantly, because also mf[["(weights)"]] will return NULL without a warning for a model/data frame, and it seems it does so also for tibbles. > Might a patch be accepted ... ? That would not be necessary. There's one remaining problem however: `$` access is clearly faster than `[[` for small data frames (because `$` is a primitive function doing everything in C, whereas `[[` calls the R level data frame method ). Faster in both cases, i.e., when there *is* a column and when there is none (and NULL is returned), e.g., for the first case> system.time(for(i in 1:20000) df[["a"]])user system elapsed 0.064 0.000 0.065> system.time(for(i in 1:20000) df$a)user system elapsed 0.009 0.000 0.009 So that's probably been the reason why `$` has been prefered? Martin > cheers > Ben Bolker
tim@t@yior m@iii@g oii hidde@eieph@@ts@co@uk
2022-Feb-03 11:30 UTC
[Rd] model.weights and model.offset: request for adjustment
> On 03/02/2022 11:14 Martin Maechler <maechler at stat.math.ethz.ch> wrote: > > > >>>>> Ben Bolker > >>>>> on Tue, 1 Feb 2022 21:21:46 -0500 writes: > > > The model.weights() and model.offset() functions from the 'stats' > > package index possibly-missing elements of a data frame via $, e.g. > > > x$"(offset)" > > x$"(weights)" > > > This returns NULL without comment when x is a data frame: > > > x <- data.frame(a=1) > > x$"(offset)" ## NULL > > x$"(weights)" ## NULL > > > However, when x is a tibble we get a warning as well: > > > x <- tibble::as_tibble(x) > > x$"(offset)" > > ## NULL > > ## Warning message: > > ## Unknown or uninitialised column: `(offset)`. > > > I know it's not R-core's responsibility to manage forward > > compatibility with tibbles, but in this case [[-indexing would seem to > > be better practice in any case. > > Yes, I would agree: we should use [[ instead of $ here > in order to force exact matching just as principle > > Importantly, because also mf[["(weights)"]] > will return NULL without a warning for a model/data frame, and > it seems it does so also for tibbles. > > > Might a patch be accepted ... ? > > That would not be necessary. > > There's one remaining problem however: > `$` access is clearly faster than `[[` for small data frames > (because `$` is a primitive function doing everything in C, > whereas `[[` calls the R level data frame method ). > > Faster in both cases, i.e., when there *is* a column and when there > is none (and NULL is returned), e.g., for the first case > > > system.time(for(i in 1:20000) df[["a"]]) > user system elapsed > 0.064 0.000 0.065 > > system.time(for(i in 1:20000) df$a) > user system elapsed > 0.009 0.000 0.009 > > So that's probably been the reason why `$` has been prefered?Would .subset2(df, "a) be preferable? R> df <- mtcars R> system.time(for(i in 1:20000) df[["hp"]]) user system elapsed 0.078 0.000 0.078 R> system.time(for(i in 1:20000) df$hp) user system elapsed 0.011 0.000 0.010 R> system.time(for(i in 1:20000) .subset2(df,"hp")) user system elapsed 0.004 0.000 0.004 Tim