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William Dunlap

2020-Jun-19 16:20 UTC

[R] Strange behavior when sampling rows of a data frame

The first subscript argument is getting evaluated twice.> trace(sample)
> set.seed(2020); df[i<-sample(10,3), ]$Treated <- TRUEtrace: sample(10, 3)
trace: sample(10, 3)> i
[1]  1 10  4> set.seed(2020); sample(10,3)trace: sample(10, 3)
[1] 7 6 8> sample(10,3)trace: sample(10, 3)
[1]  1 10  4

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Fri, Jun 19, 2020 at 8:46 AM Rui Barradas <ruipbarradas at sapo.pt>
wrote:
> Hello,
>
> I don't have an answer on the reason why this happens but it seems like
> a bug. Where?
>
> In which of  `[<-.data.frame` or `[<-.default`?
>
> A solution is to subset and assign the vector:
>
>
> set.seed(2020)
> df2 <- data.frame(unit = 1:10)
> df2$treated <- FALSE
>
> df2$treated[sample(nrow(df2), 3)] <- TRUE
> df2
> #  unit treated
> #1     1   FALSE
> #2     2   FALSE
> #3     3   FALSE
> #4     4   FALSE
> #5     5   FALSE
> #6     6    TRUE
> #7     7    TRUE
> #8     8    TRUE
> #9     9   FALSE
> #10   10   FALSE
>
>
> Or
>
>
> set.seed(2020)
> df3 <- data.frame(unit = 1:10)
> df3$treated <- FALSE
>
> df3[sample(nrow(df3), 3), "treated"] <- TRUE
> df3
> # result as expected
>
>
> Hope this helps,
>
> Rui  Barradas
>
>
>
> ?s 13:49 de 19/06/2020, S?bastien Lahaie escreveu:
> > I ran into some strange behavior in R when trying to assign a
treatment
> to
> > rows in a data frame. I'm wondering whether any R experts can
explain
> > what's going on.
> >
> > First, let's assign a treatment to 3 out of 10 rows as follows.
> >
> >> df <- data.frame(unit = 1:10)
> >> df$treated <- FALSE
> >> s <- sample(nrow(df), 3)
> >> df[s,]$treated <- TRUE
> >> df
> >     unit treated
> >
> > 1     1   FALSE
> >
> > 2     2    TRUE
> >
> > 3     3   FALSE
> >
> > 4     4   FALSE
> >
> > 5     5    TRUE
> >
> > 6     6   FALSE
> >
> > 7     7    TRUE
> >
> > 8     8   FALSE
> >
> > 9     9   FALSE
> >
> > 10   10   FALSE
> >
> > This is as expected. Now we'll just skip the intermediate step of
saving
> > the sampled indices, and apply the treatment directly as follows.
> >
> >> df <- data.frame(unit = 1:10)
> >> df$treated <- FALSE
> >> df[sample(nrow(df), 3),]$treated <- TRUE
> >> df
> >     unit treated
> >
> > 1     6    TRUE
> >
> > 2     2   FALSE
> >
> > 3     3   FALSE
> >
> > 4     9    TRUE
> >
> > 5     5   FALSE
> >
> > 6     6   FALSE
> >
> > 7     7   FALSE
> >
> > 8     5    TRUE
> >
> > 9     9   FALSE
> >
> > 10   10   FALSE
> >
> > Now the data frame still has 10 rows with 3 assigned to the treatment.
> But
> > the units are garbled. Units 1 and 4 have disappeared, for instance,
and
> > there are duplicates for 6 and 9, one assigned to treatment and the
other
> > to control. Why would this happen?
> >
> > Thanks,
> > Sebastien
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > 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.
>
> --
> Este e-mail foi verificado em termos de v?rus pelo software antiv?rus
> Avast.
> https://www.avast.com/antivirus
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.
>
	[[alternative HTML version deleted]]

Rui Barradas

2020-Jun-19 17:37 UTC

head link

[R] Strange behavior when sampling rows of a data frame

Hello,


Thanks, I hadn't thought of that.

But, why? Is it evaluated once before assignment and a second time when 
the assignment occurs?

To trace both sample and `[<-` gives 2 calls to sample.


trace(sample)
trace(`[<-`)
df[sample(nrow(df), 3),]$treated <- TRUE
trace: sample(nrow(df), 3)
trace: `[<-`(`*tmp*`, sample(nrow(df), 3), , value = list(unit = c(7L,
6L, 8L), treated = c(TRUE, TRUE, TRUE)))
trace: sample(nrow(df), 3)


Regards,

Rui Barradas


?s 17:20 de 19/06/2020, William Dunlap escreveu:> The first subscript argument is getting evaluated twice.
> > trace(sample)
> > set.seed(2020); df[i<-sample(10,3), ]$Treated <- TRUE
> trace: sample(10, 3)
> trace: sample(10, 3)
> > i
> [1] ?1 10 ?4
> > set.seed(2020); sample(10,3)
> trace: sample(10, 3)
> [1] 7 6 8
> > sample(10,3)
> trace: sample(10, 3)
> [1] ?1 10 ?4
>
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com <http://tibco.com>
>
>
> On Fri, Jun 19, 2020 at 8:46 AM Rui Barradas <ruipbarradas at sapo.pt 
> <mailto:ruipbarradas at sapo.pt>> wrote:
>
>     Hello,
>
>     I don't have an answer on the reason why this happens but it seems
>     like
>     a bug. Where?
>
>     In which of? `[<-.data.frame` or `[<-.default`?
>
>     A solution is to subset and assign the vector:
>
>
>     set.seed(2020)
>     df2 <- data.frame(unit = 1:10)
>     df2$treated <- FALSE
>
>     df2$treated[sample(nrow(df2), 3)] <- TRUE
>     df2
>     #? unit treated
>     #1???? 1?? FALSE
>     #2???? 2?? FALSE
>     #3???? 3?? FALSE
>     #4???? 4?? FALSE
>     #5???? 5?? FALSE
>     #6???? 6??? TRUE
>     #7???? 7??? TRUE
>     #8???? 8??? TRUE
>     #9???? 9?? FALSE
>     #10?? 10?? FALSE
>
>
>     Or
>
>
>     set.seed(2020)
>     df3 <- data.frame(unit = 1:10)
>     df3$treated <- FALSE
>
>     df3[sample(nrow(df3), 3), "treated"] <- TRUE
>     df3
>     # result as expected
>
>
>     Hope this helps,
>
>     Rui? Barradas
>
>
>
>     ?s 13:49 de 19/06/2020, S?bastien Lahaie escreveu:
>     > I ran into some strange behavior in R when trying to assign a
>     treatment to
>     > rows in a data frame. I'm wondering whether any R experts can
>     explain
>     > what's going on.
>     >
>     > First, let's assign a treatment to 3 out of 10 rows as
follows.
>     >
>     >> df <- data.frame(unit = 1:10)
>     >> df$treated <- FALSE
>     >> s <- sample(nrow(df), 3)
>     >> df[s,]$treated <- TRUE
>     >> df
>     >? ? ?unit treated
>     >
>     > 1? ? ?1? ?FALSE
>     >
>     > 2? ? ?2? ? TRUE
>     >
>     > 3? ? ?3? ?FALSE
>     >
>     > 4? ? ?4? ?FALSE
>     >
>     > 5? ? ?5? ? TRUE
>     >
>     > 6? ? ?6? ?FALSE
>     >
>     > 7? ? ?7? ? TRUE
>     >
>     > 8? ? ?8? ?FALSE
>     >
>     > 9? ? ?9? ?FALSE
>     >
>     > 10? ?10? ?FALSE
>     >
>     > This is as expected. Now we'll just skip the intermediate step
>     of saving
>     > the sampled indices, and apply the treatment directly as follows.
>     >
>     >> df <- data.frame(unit = 1:10)
>     >> df$treated <- FALSE
>     >> df[sample(nrow(df), 3),]$treated <- TRUE
>     >> df
>     >? ? ?unit treated
>     >
>     > 1? ? ?6? ? TRUE
>     >
>     > 2? ? ?2? ?FALSE
>     >
>     > 3? ? ?3? ?FALSE
>     >
>     > 4? ? ?9? ? TRUE
>     >
>     > 5? ? ?5? ?FALSE
>     >
>     > 6? ? ?6? ?FALSE
>     >
>     > 7? ? ?7? ?FALSE
>     >
>     > 8? ? ?5? ? TRUE
>     >
>     > 9? ? ?9? ?FALSE
>     >
>     > 10? ?10? ?FALSE
>     >
>     > Now the data frame still has 10 rows with 3 assigned to the
>     treatment. But
>     > the units are garbled. Units 1 and 4 have disappeared, for
>     instance, and
>     > there are duplicates for 6 and 9, one assigned to treatment and
>     the other
>     > to control. Why would this happen?
>     >
>     > Thanks,
>     > Sebastien
>     >
>     >? ? ? ?[[alternative HTML version deleted]]
>     >
>     > ______________________________________________
>     > R-help at r-project.org <mailto:R-help at r-project.org>
mailing list
>     -- To UNSUBSCRIBE and more, see
>     > 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.
>
>     -- 
>     Este e-mail foi verificado em termos de v?rus pelo software
>     antiv?rus Avast.
>     https://www.avast.com/antivirus
>
>     ______________________________________________
>     R-help at r-project.org <mailto:R-help at r-project.org> mailing
list --
>     To UNSUBSCRIBE and more, see
>     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.
>
-- 
Este e-mail foi verificado em termos de v?rus pelo software antiv?rus Avast.
https://www.avast.com/antivirus

William Dunlap

2020-Jun-19 17:42 UTC

head link

[R] Strange behavior when sampling rows of a data frame

It is a bug that has been present in R since at least R-2.14.0 (the oldest
that I have installed on my laptop).

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Fri, Jun 19, 2020 at 10:37 AM Rui Barradas <ruipbarradas at sapo.pt>
wrote:
> Hello,
>
>
> Thanks, I hadn't thought of that.
>
> But, why? Is it evaluated once before assignment and a second time when
> the assignment occurs?
>
> To trace both sample and `[<-` gives 2 calls to sample.
>
>
> trace(sample)
> trace(`[<-`)
> df[sample(nrow(df), 3),]$treated <- TRUE
> trace: sample(nrow(df), 3)
> trace: `[<-`(`*tmp*`, sample(nrow(df), 3), , value = list(unit = c(7L,
> 6L, 8L), treated = c(TRUE, TRUE, TRUE)))
> trace: sample(nrow(df), 3)
>
>
> Regards,
>
> Rui Barradas
>
>
> ?s 17:20 de 19/06/2020, William Dunlap escreveu:
> > The first subscript argument is getting evaluated twice.
> > > trace(sample)
> > > set.seed(2020); df[i<-sample(10,3), ]$Treated <- TRUE
> > trace: sample(10, 3)
> > trace: sample(10, 3)
> > > i
> > [1]  1 10  4
> > > set.seed(2020); sample(10,3)
> > trace: sample(10, 3)
> > [1] 7 6 8
> > > sample(10,3)
> > trace: sample(10, 3)
> > [1]  1 10  4
> >
> > Bill Dunlap
> > TIBCO Software
> > wdunlap tibco.com <http://tibco.com>
> >
> >
> > On Fri, Jun 19, 2020 at 8:46 AM Rui Barradas <ruipbarradas at
sapo.pt
> > <mailto:ruipbarradas at sapo.pt>> wrote:
> >
> >     Hello,
> >
> >     I don't have an answer on the reason why this happens but it
seems
> >     like
> >     a bug. Where?
> >
> >     In which of  `[<-.data.frame` or `[<-.default`?
> >
> >     A solution is to subset and assign the vector:
> >
> >
> >     set.seed(2020)
> >     df2 <- data.frame(unit = 1:10)
> >     df2$treated <- FALSE
> >
> >     df2$treated[sample(nrow(df2), 3)] <- TRUE
> >     df2
> >     #  unit treated
> >     #1     1   FALSE
> >     #2     2   FALSE
> >     #3     3   FALSE
> >     #4     4   FALSE
> >     #5     5   FALSE
> >     #6     6    TRUE
> >     #7     7    TRUE
> >     #8     8    TRUE
> >     #9     9   FALSE
> >     #10   10   FALSE
> >
> >
> >     Or
> >
> >
> >     set.seed(2020)
> >     df3 <- data.frame(unit = 1:10)
> >     df3$treated <- FALSE
> >
> >     df3[sample(nrow(df3), 3), "treated"] <- TRUE
> >     df3
> >     # result as expected
> >
> >
> >     Hope this helps,
> >
> >     Rui  Barradas
> >
> >
> >
> >     ?s 13:49 de 19/06/2020, S?bastien Lahaie escreveu:
> >     > I ran into some strange behavior in R when trying to assign a
> >     treatment to
> >     > rows in a data frame. I'm wondering whether any R experts
can
> >     explain
> >     > what's going on.
> >     >
> >     > First, let's assign a treatment to 3 out of 10 rows as
follows.
> >     >
> >     >> df <- data.frame(unit = 1:10)
> >     >> df$treated <- FALSE
> >     >> s <- sample(nrow(df), 3)
> >     >> df[s,]$treated <- TRUE
> >     >> df
> >     >     unit treated
> >     >
> >     > 1     1   FALSE
> >     >
> >     > 2     2    TRUE
> >     >
> >     > 3     3   FALSE
> >     >
> >     > 4     4   FALSE
> >     >
> >     > 5     5    TRUE
> >     >
> >     > 6     6   FALSE
> >     >
> >     > 7     7    TRUE
> >     >
> >     > 8     8   FALSE
> >     >
> >     > 9     9   FALSE
> >     >
> >     > 10   10   FALSE
> >     >
> >     > This is as expected. Now we'll just skip the intermediate
step
> >     of saving
> >     > the sampled indices, and apply the treatment directly as
follows.
> >     >
> >     >> df <- data.frame(unit = 1:10)
> >     >> df$treated <- FALSE
> >     >> df[sample(nrow(df), 3),]$treated <- TRUE
> >     >> df
> >     >     unit treated
> >     >
> >     > 1     6    TRUE
> >     >
> >     > 2     2   FALSE
> >     >
> >     > 3     3   FALSE
> >     >
> >     > 4     9    TRUE
> >     >
> >     > 5     5   FALSE
> >     >
> >     > 6     6   FALSE
> >     >
> >     > 7     7   FALSE
> >     >
> >     > 8     5    TRUE
> >     >
> >     > 9     9   FALSE
> >     >
> >     > 10   10   FALSE
> >     >
> >     > Now the data frame still has 10 rows with 3 assigned to the
> >     treatment. But
> >     > the units are garbled. Units 1 and 4 have disappeared, for
> >     instance, and
> >     > there are duplicates for 6 and 9, one assigned to treatment
and
> >     the other
> >     > to control. Why would this happen?
> >     >
> >     > Thanks,
> >     > Sebastien
> >     >
> >     >       [[alternative HTML version deleted]]
> >     >
> >     > ______________________________________________
> >     > R-help at r-project.org <mailto:R-help at
r-project.org> mailing list
> >     -- To UNSUBSCRIBE and more, see
> >     > 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.
> >
> >     --
> >     Este e-mail foi verificado em termos de v?rus pelo software
> >     antiv?rus Avast.
> >     https://www.avast.com/antivirus
> >
> >     ______________________________________________
> >     R-help at r-project.org <mailto:R-help at r-project.org>
mailing list --
> >     To UNSUBSCRIBE and more, see
> >     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.
> >
>
> --
> Este e-mail foi verificado em termos de v?rus pelo software antiv?rus
> Avast.
> https://www.avast.com/antivirus
>
>
	[[alternative HTML version deleted]]

R help - Jun 2020 - Strange behavior when sampling rows of a data frame

[R] Strange behavior when sampling rows of a data frame

[R] Strange behavior when sampling rows of a data frame

[R] Strange behavior when sampling rows of a data frame