Re: [R] Unexpected behavior looping through sequence of dates
Thanks for the clarification, Luke.
That is really counter-intuitive behavior. I 100% agree with you that the "for"
documentation should state that assumption explicitly.
I would also like to suggest changing the "for" implementation to issue a
warning if the "seq" argument is a vector of a non-primitive type. That would
have saved me a few hours of debugging in the last few days, so I imagine it
must be relevant for more people as well.
--
Alexandre Sieira
CISA, CISSP, ISO 27001 Lead Auditor
"The truth is rarely pure and never simple."
Oscar Wilde, The Importance of Being Earnest, 1895, Act I
Sent with Sparrow (http://www.sparrowmailapp.com/?sig)
On Saturday, 9 de March de 2013 at 13:10, luke-tier...@uiowa.edu wrote:
> R's for loop is only designed to iterato over primitive types. The
> help file says of the seq argument:
>
> seq: An expression evaluating to a vector (including a list and an
> expression) or to a pairlist or ¡NULL¢. A factor value will
> be coerced to a character vector.
>
> [This could be more emphatic by stating that any class attributes are
> igonred or something of that nature.]
>
> Having for() do anything else would require designing an iteration
> protocol -- probably would be nice in principle but not easy to do.
>
> Best,
>
> luke
>
> On Sat, 9 Mar 2013, Peter Ehlers wrote:
>
> > On 2013-03-09 11:14, R. Michael Weylandt wrote:
> > > On Sat, Mar 9, 2013 at 6:50 PM, David Winsemius > > (mailto:dwinsem...@comcast.net)>
> > > wrote:
> > > > I was unable to find the reason for the original coercion in the
> > > > help("for") page or the R
> > > > Language Definition entry regarding for-loops. On the hunch that
> > > > coercion
> > > > via as.vector
> > > > might be occurring,
> > >
> > >
> > >
> > > Behaviorally, it seems to, but the code for do_for in eval.c has
> > > factors special-cased to call
> > > asCharacterFactor so that might not be a robust detail to rely on. The
> > > relevant behavior seems instead to be that there's a
> > > switch on val_type which creates the loop index but doesn't copy all
> > > attributes (like class)
> > >
> > > Note that this means a user's as.vector wouldn't be called here:
> > >
> > > as.vector.flub <- function(x, ...) letters[x]
> > >
> > > foo <- 1:5
> > > class(foo) <- "flub"
> > >
> > > as.vector(foo)
> > >
> > > for(j in foo) {print(j); print(class(j))}
> > >
> > > as.vector.grub <- function(x, ...) match(x, letters)
> > >
> > > bar <- letters[1:5]
> > > class(bar) <- "grub"
> > >
> > > as.vector(bar)
> > >
> > > for(j in bar) {print(j); print(class(j))}
> > >
> > > Cheers,
> > > Michael
> >
> >
> >
> > I think that Michael is right - the problem is with val_type
> > in the do_for code.
> >
> > Here's a simplified version of Alexandre's example:
> >
> > d <- as.Date("2013-03-10")
> > for(i in seq_along(d)) print(i)
> > #[1] 1
> >
> > for(i in d) print(i)
> > #[1] 15774
> > where we might have expected to see "2013-03-10".
> >
> > The essential line in the do_for code seems to me to be:
> >
> > val_type = TYPEOF(val);
> >
> > ?typeof tells us that R does not have a 'date' type, so:
> >
> > typeof(d)
> > #[1] "double"
> >
> > And the for-loop results follow.
> >
> > Peter Ehlers
> >
> > __
> > R-help@r-project.org (mailto: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.
>
>
>
> --
> Luke Tierney
> Chair, Statistics and Actuarial Science
> Ralph E. Wareham Professor of Mathematical Sciences
> University of Iowa Phone: 319-335-3386
> Department of Statistics and Fax: 319-335-3017
> Actuarial Science
> 241 Schaeffer Hall email: luke-tier...@uiowa.edu
> (mailto:luke-tier...@uiowa.edu)
> Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
__
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.
Re: [R] Unexpected behavior looping through sequence of dates
On Sat, 9 Mar 2013, Alexandre Sieira wrote:
Thanks for the clarification, Luke.
That is really counter-intuitive behavior. I 100% agree with you that the "for"
documentation should state that assumption explicitly.
I would also like to suggest changing the "for" implementation to issue a warning if the
"seq" argument is a vector of a non-primitive type. That would have saved me a few hours
of debugging in the last few days, so I imagine it must be relevant for more people as well.
Issuing a warning unconditioally would result in far to many spurious
warnings. for() works perfecly fine now for most objects with a class
attribute. I don't see a reasonable way to detect the subset of cases
where this is not true (other than registering a list of classes for()
should warn about, which might be feasible, though might refult in a
significant performance hit.)
Best,
luke
--
Alexandre Sieira
CISA, CISSP, ISO 27001 Lead Auditor
"The truth is rarely pure and never simple."
Oscar Wilde, The Importance of Being Earnest, 1895, Act I
Sent with Sparrow (http://www.sparrowmailapp.com/?sig)
On Saturday, 9 de March de 2013 at 13:10, luke-tier...@uiowa.edu wrote:
R's for loop is only designed to iterato over primitive types. The
help file says of the seq argument:
seq: An expression evaluating to a vector (including a list and an
expression) or to a pairlist or ¡NULL¢. A factor value will
be coerced to a character vector.
[This could be more emphatic by stating that any class attributes are
igonred or something of that nature.]
Having for() do anything else would require designing an iteration
protocol -- probably would be nice in principle but not easy to do.
Best,
luke
On Sat, 9 Mar 2013, Peter Ehlers wrote:
On 2013-03-09 11:14, R. Michael Weylandt wrote:
On Sat, Mar 9, 2013 at 6:50 PM, David Winsemius mailto:dwinsem...@comcast.net)>
wrote:
I was unable to find the reason for the original coercion in the
help("for") page or the R
Language Definition entry regarding for-loops. On the hunch that coercion
via as.vector
might be occurring,
Behaviorally, it seems to, but the code for do_for in eval.c has
factors special-cased to call
asCharacterFactor so that might not be a robust detail to rely on. The
relevant behavior seems instead to be that there's a
switch on val_type which creates the loop index but doesn't copy all
attributes (like class)
Note that this means a user's as.vector wouldn't be called here:
as.vector.flub <- function(x, ...) letters[x]
foo <- 1:5
class(foo) <- "flub"
as.vector(foo)
for(j in foo) {print(j); print(class(j))}
as.vector.grub <- function(x, ...) match(x, letters)
bar <- letters[1:5]
class(bar) <- "grub"
as.vector(bar)
for(j in bar) {print(j); print(class(j))}
Cheers,
Michael
I think that Michael is right - the problem is with val_type
in the do_for code.
Here's a simplified version of Alexandre's example:
d <- as.Date("2013-03-10")
for(i in seq_along(d)) print(i)
#[1] 1
for(i in d) print(i)
#[1] 15774
where we might have expected to see "2013-03-10".
The essential line in the do_for code seems to me to be:
val_type = TYPEOF(val);
?typeof tells us that R does not have a 'date' type, so:
typeof(d)
#[1] "double"
And the for-loop results follow.
Peter Ehlers
__
R-help@r-project.org (mailto: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.
--
Luke Tierney
Chair, Statistics and Actuarial Science
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa Phone: 319-335-3386
Department of Statistics and Fax: 319-335-3017
Actuarial Science
241 Schaeffer Hall email: luke-tier...@uiowa.edu (mailto:luke-tier...@uiowa.edu)
Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
--
Luke Tierney
Chair, Statistics and Actuarial Science
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa Phone: 319-335-3386
Department of Statistics andFax: 319-335-3017
Actuarial Science
241 Schaeffer Hall email: luke-tier...@uiowa.edu
Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu__
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.
Re: [R] Unexpected behavior looping through sequence of dates
On Mar 9, 2013, at 1:10 PM, wrote:
> R's for loop is only designed to iterato over primitive types. The
> help file says of the seq argument:
>
> seq: An expression evaluating to a vector (including a list and an
> expression) or to a pairlist or ‘NULL’. A factor value will
> be coerced to a character vector.
>
> [This could be more emphatic by stating that any class attributes are
> igonred or something of that nature.]
>
> Having for() do anything else would require designing an iteration
> protocol -- probably would be nice in principle but not easy to do.
except it works fine with lists:
for ( i in as.list(seq(Sys.Date(), length=4,by=1) ) ) print(class(i))
[1] "Date"
[1] "Date"
[1] "Date"
[1] "Date"
>
> Best,
>
> luke
>
> On Sat, 9 Mar 2013, Peter Ehlers wrote:
>
>> On 2013-03-09 11:14, R. Michael Weylandt wrote:
>>> On Sat, Mar 9, 2013 at 6:50 PM, David Winsemius
>>> wrote:
I was unable to find the reason for the original coercion in the
help("for") page or the R
Language Definition entry regarding for-loops. On the hunch that coercion
via as.vector
might be occurring,
>>> Behaviorally, it seems to, but the code for do_for in eval.c has
>>> factors special-cased to call
>>> asCharacterFactor so that might not be a robust detail to rely on. The
>>> relevant behavior seems instead to be that there's a
>>> switch on val_type which creates the loop index but doesn't copy all
>>> attributes (like class)
>>> Note that this means a user's as.vector wouldn't be called here:
>>> as.vector.flub <- function(x, ...) letters[x]
>>> foo <- 1:5
>>> class(foo) <- "flub"
>>> as.vector(foo)
>>> for(j in foo) {print(j); print(class(j))}
>>> as.vector.grub <- function(x, ...) match(x, letters)
>>> bar <- letters[1:5]
>>> class(bar) <- "grub"
>>> as.vector(bar)
>>> for(j in bar) {print(j); print(class(j))}
>>> Cheers,
>>> Michael
>>
>> I think that Michael is right - the problem is with val_type
>> in the do_for code.
>>
>> Here's a simplified version of Alexandre's example:
>>
>> d <- as.Date("2013-03-10")
>> for(i in seq_along(d)) print(i)
>> #[1] 1
>>
>> for(i in d) print(i)
>> #[1] 15774
>> where we might have expected to see "2013-03-10".
>>
>> The essential line in the do_for code seems to me to be:
>>
>> val_type = TYPEOF(val);
>>
>> ?typeof tells us that R does not have a 'date' type, so:
>>
>> typeof(d)
>> #[1] "double"
>>
>> And the for-loop results follow.
>>
>> Peter Ehlers
>>
>> __
>> 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.
>>
>
> --
> Luke Tierney
> Chair, Statistics and Actuarial Science
> Ralph E. Wareham Professor of Mathematical Sciences
> University of Iowa Phone: 319-335-3386
> Department of Statistics andFax: 319-335-3017
> Actuarial Science
> 241 Schaeffer Hall email: luke-tier...@uiowa.edu
> Iowa City, IA 52242 WWW:
> http://www.stat.uiowa.edu__
> 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.
David Winsemius
Alameda, CA, USA
__
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.
Re: [R] Unexpected behavior looping through sequence of dates
R's for loop is only designed to iterato over primitive types. The
help file says of the seq argument:
seq: An expression evaluating to a vector (including a list and an
expression) or to a pairlist or ‘NULL’. A factor value will
be coerced to a character vector.
[This could be more emphatic by stating that any class attributes are
igonred or something of that nature.]
Having for() do anything else would require designing an iteration
protocol -- probably would be nice in principle but not easy to do.
Best,
luke
On Sat, 9 Mar 2013, Peter Ehlers wrote:
On 2013-03-09 11:14, R. Michael Weylandt wrote:
On Sat, Mar 9, 2013 at 6:50 PM, David Winsemius
wrote:
I was unable to find the reason for the original coercion in the
help("for") page or the R
Language Definition entry regarding for-loops. On the hunch that coercion
via as.vector
might be occurring,
Behaviorally, it seems to, but the code for do_for in eval.c has
factors special-cased to call
asCharacterFactor so that might not be a robust detail to rely on. The
relevant behavior seems instead to be that there's a
switch on val_type which creates the loop index but doesn't copy all
attributes (like class)
Note that this means a user's as.vector wouldn't be called here:
as.vector.flub <- function(x, ...) letters[x]
foo <- 1:5
class(foo) <- "flub"
as.vector(foo)
for(j in foo) {print(j); print(class(j))}
as.vector.grub <- function(x, ...) match(x, letters)
bar <- letters[1:5]
class(bar) <- "grub"
as.vector(bar)
for(j in bar) {print(j); print(class(j))}
Cheers,
Michael
I think that Michael is right - the problem is with val_type
in the do_for code.
Here's a simplified version of Alexandre's example:
d <- as.Date("2013-03-10")
for(i in seq_along(d)) print(i)
#[1] 1
for(i in d) print(i)
#[1] 15774
where we might have expected to see "2013-03-10".
The essential line in the do_for code seems to me to be:
val_type = TYPEOF(val);
?typeof tells us that R does not have a 'date' type, so:
typeof(d)
#[1] "double"
And the for-loop results follow.
Peter Ehlers
__
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.
--
Luke Tierney
Chair, Statistics and Actuarial Science
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa Phone: 319-335-3386
Department of Statistics andFax: 319-335-3017
Actuarial Science
241 Schaeffer Hall email: luke-tier...@uiowa.edu
Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu__
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.
Re: [R] Unexpected behavior looping through sequence of dates
On 2013-03-09 11:14, R. Michael Weylandt wrote:
On Sat, Mar 9, 2013 at 6:50 PM, David Winsemius wrote:
I was unable to find the reason for the original coercion in the help("for")
page or the R
Language Definition entry regarding for-loops. On the hunch that coercion via
as.vector
might be occurring,
Behaviorally, it seems to, but the code for do_for in eval.c has
factors special-cased to call
asCharacterFactor so that might not be a robust detail to rely on. The
relevant behavior seems instead to be that there's a
switch on val_type which creates the loop index but doesn't copy all
attributes (like class)
Note that this means a user's as.vector wouldn't be called here:
as.vector.flub <- function(x, ...) letters[x]
foo <- 1:5
class(foo) <- "flub"
as.vector(foo)
for(j in foo) {print(j); print(class(j))}
as.vector.grub <- function(x, ...) match(x, letters)
bar <- letters[1:5]
class(bar) <- "grub"
as.vector(bar)
for(j in bar) {print(j); print(class(j))}
Cheers,
Michael
I think that Michael is right - the problem is with val_type
in the do_for code.
Here's a simplified version of Alexandre's example:
d <- as.Date("2013-03-10")
for(i in seq_along(d)) print(i)
#[1] 1
for(i in d) print(i)
#[1] 15774
where we might have expected to see "2013-03-10".
The essential line in the do_for code seems to me to be:
val_type = TYPEOF(val);
?typeof tells us that R does not have a 'date' type, so:
typeof(d)
#[1] "double"
And the for-loop results follow.
Peter Ehlers
__
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.
Re: [R] Unexpected behavior looping through sequence of dates
On Sat, Mar 9, 2013 at 6:50 PM, David Winsemius wrote:
> I was unable to find the reason for the original coercion in the help("for")
> page or the R
> Language Definition entry regarding for-loops. On the hunch that coercion via
> as.vector
> might be occurring,
Behaviorally, it seems to, but the code for do_for in eval.c has
factors special-cased to call
asCharacterFactor so that might not be a robust detail to rely on. The
relevant behavior seems instead to be that there's a
switch on val_type which creates the loop index but doesn't copy all
attributes (like class)
Note that this means a user's as.vector wouldn't be called here:
as.vector.flub <- function(x, ...) letters[x]
foo <- 1:5
class(foo) <- "flub"
as.vector(foo)
for(j in foo) {print(j); print(class(j))}
as.vector.grub <- function(x, ...) match(x, letters)
bar <- letters[1:5]
class(bar) <- "grub"
as.vector(bar)
for(j in bar) {print(j); print(class(j))}
Cheers,
Michael
__
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.
Re: [R] Unexpected behavior looping through sequence of dates
On Mar 9, 2013, at 9:24 AM, Alexandre Sieira wrote:
> I understand that the two following loops should produce the exact same
> output. However, they do not. It appears that looping directly through the
> sequence of Date objects somehow makes them be coerced to numeric:
>
>> date1 = "20130301"
>> date2 = "20130302"
>>
>> d1 = as.Date(date1, format="%Y%m%d", tz="GMT")
>> d2 = as.Date(date2, format="%Y%m%d", tz="GMT")
>>
>> range = seq(from=d1, to=d2, by="day")
>> for (i in 1:length(range)) print(class(range[i]))
>
> [1] "Date"
> [1] "Date"
>>
>> for (i in seq(from=d1, to=d2, by="day")) print(class(i))
> [1] "numeric"
> [1] "numeric"
>
> This is output from R version 2.15.2 (2012-10-26) on Mac OS X 10.8.2.
>
> Is this expected behavior?
It wasn't expected by me either, but it is what both my Mac R 2.15.3 and my
Windows(32bit) 2.15.1 display. If you put those dates in a list, you do not get
the coercion:
> for (i in list(d1,d2)) print(class(i))
[1] "Date"
[1] "Date"
I was unable to find the reason for the original coercion in the help("for")
page or the R Language Definition entry regarding for-loops. On the hunch that
coercion via as.vector might be occurring, I tried with with a factor vector
and did see that it was coerced to "character" which is the behavior that would
be expected if that were happening behind the scenes:
ff <- factor(letters[1:3])
as.vector(ff)
#[1] "a" "b" "c"
for (i in ff) print(class(i))
#[1] "character"
#[1] "character"
#[1] "character"
(I also tried searching for loop in the R Internals document and found nothing
that explained this to me.)
--
David.
> --
> Alexandre Sieira
> CISA, CISSP, ISO 27001 Lead Auditor
>
> "The truth is rarely pure and never simple."
> Oscar Wilde, The Importance of Being Earnest, 1895, Act I
>
>
> Sent with Sparrow (http://www.sparrowmailapp.com/?sig)
>
> __
> 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.
David Winsemius
Alameda, CA, USA
__
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.
