[R] Is this foreach behaviour correct?

[William Dunlap]

Note that in the OP's example c.Date is never invoked.  c.Date is called if
.combine
calls c rather than if .combine is c:

> library(zoo)
> trace(c.Date, quote(print(sys.call())))
Tracing function "c.Date" in package "base"
[1] "c.Date"
> foreach(i=10000:10003, .combine=c) %do% { as.Date(i) }
[1] 10000 10001 10002 10003
> foreach(i=10000:10003, .combine=function(...)c(...)) %do% { as.Date(i) }
Tracing c.Date(...) on entry
eval(expr, envir, enclos)
Tracing c.Date(...) on entry
eval(expr, envir, enclos)
Tracing c.Date(...) on entry
eval(expr, envir, enclos)
[1] "1997-05-19" "1997-05-20" "1997-05-21" "1997-05-22"


Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Sun, Nov 6, 2016 at 2:20 PM, Duncan Murdoch <murdoch.duncan at gmail.com>
wrote:

> On 06/11/2016 5:02 PM, Jim Lemon wrote:
>
>> hi James,
>> I think you have to have a starting date ("origin") for as.Date to
>> convert numbers to dates.
>>
>
> That's true with the function in the base package, but the zoo package
> also has an as.Date() function, which defaults the origin to "1970-01-01".
> If James is using zoo his code would be okay.  If he's not, he would have
> got an error, so I think he must have been.
>
> Duncan Murdoch
>
>
>
>> Jim
>>
>> On Sun, Nov 6, 2016 at 12:10 PM, James Hirschorn
>> <james.hirschorn at hotmail.com> wrote:
>>
>>> This seemed odd so I wanted to check:
>>>
>>>  > x <- foreach(i=10000:10100, .combine='c') %do% { as.Date(i) }
>>>
>>> yields a numeric vector for x:
>>>
>>>  > class(x)
>>> [1] "numeric"
>>>
>>> Should it not be a vector of Date?
>>>
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>>
>> ______________________________________________
>> 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/posti
>> ng-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
> ______________________________________________
> 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/posti
> ng-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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