This is completely wrong: min _is_ defined for date-times:
min(.leap.seconds)
[1] 1972-07-01 01:00:00 BST
Please do study the posting guide and do your homework before posting: you
seem unaware of what the POSIXct class is, so ?DateTimeClasses is one
place you need to start. And
Hi
I have a dataframe in which some subjects appear in more than one row. I
want to extract the subject-rows which have the minimum date per subject. I
tried the following aggregate function.
attach(dataframe.xy)
aggregate(Date,list(SubjectID),min)
Unfortunately, the format of the Date-column
Try changing the 'class' of the numeric result back to Date:
x - as.Date('2008-09-08')
x
[1] 2008-09-08
y - as.numeric(x)
y
[1] 14130
str(y)
num 14130
class(y) - Date
y
[1] 2008-09-08
str(y)
Class 'Date' num 14130
On Mon, Sep 8, 2008 at 6:38 AM, Erich Studerus
[EMAIL PROTECTED]
the rows with
minimum/earliest date per subject.
Erich
-Ursprüngliche Nachricht-
Von: jim holtman [mailto:[EMAIL PROTECTED]
Gesendet: Montag, 8. September 2008 14:24
An: Erich Studerus
Cc: r-help@r-project.org
Betreff: Re: [R] How to preserve date format while aggregating
Try changing
-Ursprüngliche Nachricht-
Von: jim holtman [mailto:[EMAIL PROTECTED]
Gesendet: Montag, 8. September 2008 14:24
An: Erich Studerus
Cc: r-help@r-project.org
Betreff: Re: [R] How to preserve date format while aggregating
Try changing the 'class' of the numeric result back to Date:
x - as.Date
-Ursprüngliche Nachricht-
Von: jim holtman [mailto:[EMAIL PROTECTED]
Gesendet: Montag, 8. September 2008 14:24
An: Erich Studerus
Cc: r-help@r-project.org
Betreff: Re: [R] How to preserve date format while aggregating
Try changing the 'class' of the numeric result back to Date:
x - as.Date
:43
An: Erich Studerus
Cc: r-help@r-project.org
Betreff: Re: [R] How to preserve date format while aggregating
Erich,
how does the data look, when it comes from SQL?
And why not extract the data with SQL directly, so you don't
have this issue in the first place?
el
on 9/8/08 3:15 PM Erich
An: Erich Studerus
Cc: r-help@r-project.org
Betreff: Re: [R] How to preserve date format while aggregating
Erich,
how does the data look, when it comes from SQL?
And why not extract the data with SQL directly, so you don't
have this issue in the first place?
el
on 9/8/08 3:15 PM Erich Studerus
with
minimum/earliest date per subject.
Erich
-Ursprüngliche Nachricht-
Von: jim holtman [mailto:[EMAIL PROTECTED]
Gesendet: Montag, 8. September 2008 14:24
An: Erich Studerus
Cc: r-help@r-project.org
Betreff: Re: [R] How to preserve date format while aggregating
Try changing the 'class
Hi Erich,
Since min() is defined for numbers and not dates, the problem is in the
min() function. min() is converting from date format to number format.
Your best bet is to make this conversion explicit...such that it is
reversable. So, convert the date into UTC, then UTC to seconds since
min does work for POSIXct and Date too:
ct - ISOdatetime(2008, 1, 1:10, 0, 0, 0)
min(ct)
[1] 2008-01-01 EST
min(as.Date(ct))
[1] 2008-01-01
On Mon, Sep 8, 2008 at 6:57 PM, Adam D. I. Kramer
[EMAIL PROTECTED] wrote:
Hi Erich,
Since min() is defined for numbers and not dates, the problem
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