R help - Jul 2011 - coordinates from locator function in POSIXct format

Dear R-list,

I have a plot with y-axis corresponding to wind measurments
and x-axis with date-time information.
When I want to identify some extrem wind events in the
wind-curve, I use locator() to get the exact
date-information, by clicking in the points in graph I?m
interested in.
I get in the R console the x and y coordinates.
The x coordinates are not in a POSIXct format, I guess R is
returning the x coordinates in a time unit as miliseconds
or something else.

Do anyone how to get the x coordinates directly in a
POSIXct format?

Thanks in advance!
Cristabel.


Cristabel Dur?n Rangel. PhD Student.
Institute of Silviculture. Faculty of Forest and
Environmental Sciences. University of Freiburg.
Germany
Telf: +49 (761) 203 8604 (ofc) 

?Man lernt die Physiognomie einer Landschaft desto besser
kennen, je genauer man die einzelnen Z?ge auffa?t, sie
untereinander vergleicht und so auf dem Wege der Analysis
den Quellen der Gen?sse nachgeht, die uns das gro?e
Naturgem?lde bietet.?
				Alexander von Humboldt, 1799

Well,if you would have had a look at ?POSIXct the documentation would 
have given
  you quite a comprehensive explanation of the meaning of the values of 
your time vector as they are the values these POSIXct values are 
actually stored in (they are seconds since 1970-01-01). Additionally you 
would have been redirected to as.POSIXct() which converts all sorts of 
objects to POSIXct. I would expect this function to return your desired 
format if you feed it with the numeric values that locator() returned.


HTH
Jannis



On 07/29/2011 03:40 PM, cristabel.duran at waldbau.uni-freiburg.de
wrote:
> Dear R-list,
>
> I have a plot with y-axis corresponding to wind measurments
> and x-axis with date-time information.
> When I want to identify some extrem wind events in the
> wind-curve, I use locator() to get the exact
> date-information, by clicking in the points in graph I?m
> interested in.
> I get in the R console the x and y coordinates.
> The x coordinates are not in a POSIXct format, I guess R is
> returning the x coordinates in a time unit as miliseconds
> or something else.
>
> Do anyone how to get the x coordinates directly in a
> POSIXct format?
>
> Thanks in advance!
> Cristabel.
>
>
> Cristabel Dur?n Rangel. PhD Student.
> Institute of Silviculture. Faculty of Forest and
> Environmental Sciences. University of Freiburg.
> Germany
> Telf: +49 (761) 203 8604 (ofc)
>
> ?Man lernt die Physiognomie einer Landschaft desto besser
> kennen, je genauer man die einzelnen Z?ge auffa?t, sie
> untereinander vergleicht und so auf dem Wege der Analysis
> den Quellen der Gen?sse nachgeht, die uns das gro?e
> Naturgem?lde bietet.?
> 				Alexander von Humboldt, 1799
>
> ______________________________________________
> R-help at 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.

Hi Janis,
thank you for you answer.

Actually already I did exactly what you said. However, when I convert 
the number of "seconds" from the first measurement (some day in July 
2010) then a I get a date in the year 2050 which is impossible. The 
latest date possible is 29March2011.

my value in ?seconds?: 1285038419
z <- 1285038419
as.POSIXct(z, origin="2010-07-15")
"2051-04-04 03:06:59 CEST"

any clue why I get this date?

I thank your help,

Cristabel.



On 07/29/2011 04:45 PM, Jannis wrote:
> Well,if you would have had a look at ?POSIXct the documentation would 
> have given
>  you quite a comprehensive explanation of the meaning of the values of 
> your time vector as they are the values these POSIXct values are 
> actually stored in (they are seconds since 1970-01-01). Additionally 
> you would have been redirected to as.POSIXct() which converts all 
> sorts of objects to POSIXct. I would expect this function to return 
> your desired format if you feed it with the numeric values that 
> locator() returned.
>
>
> HTH
> Jannis
>
>
>
> On 07/29/2011 03:40 PM, cristabel.duran at waldbau.uni-freiburg.de wrote:
>> Dear R-list,
>>
>> I have a plot with y-axis corresponding to wind measurments
>> and x-axis with date-time information.
>> When I want to identify some extrem wind events in the
>> wind-curve, I use locator() to get the exact
>> date-information, by clicking in the points in graph I?m
>> interested in.
>> I get in the R console the x and y coordinates.
>> The x coordinates are not in a POSIXct format, I guess R is
>> returning the x coordinates in a time unit as miliseconds
>> or something else.
>>
>> Do anyone how to get the x coordinates directly in a
>> POSIXct format?
>>
>> Thanks in advance!
>> Cristabel.
>>
>>
>> Cristabel Dur?n Rangel. PhD Student.
>> Institute of Silviculture. Faculty of Forest and
>> Environmental Sciences. University of Freiburg.
>> Germany
>> Telf: +49 (761) 203 8604 (ofc)
>>
>> ?Man lernt die Physiognomie einer Landschaft desto besser
>> kennen, je genauer man die einzelnen Z?ge auffa?t, sie
>> untereinander vergleicht und so auf dem Wege der Analysis
>> den Quellen der Gen?sse nachgeht, die uns das gro?e
>> Naturgem?lde bietet.?
>>                 Alexander von Humboldt, 1799
>>
>> ______________________________________________
>> R-help at 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.
>

On Jul 29, 2011, at 12:21 PM, cristabel.duran wrote:
> Hi Janis,
> thank you for you answer.
>
> Actually already I did exactly what you said. However, when I  
> convert the number of "seconds" from the first measurement (some
day
> in July 2010) then a I get a date in the year 2050 which is  
> impossible. The latest date possible is 29March2011.
>
> my value in ?seconds?: 1285038419
> z <- 1285038419
> as.POSIXct(z, origin="2010-07-15")
> "2051-04-04 03:06:59 CEST"
>
> any clue why I get this date?
Because the default origin is 1970-01-01

 > z <- 1285038419
 > as.POSIXct(z, origin="1970-01-01")
[1] "2010-09-21 04:06:59 EDT"

-- 
David.
>
> I thank your help,
>
> Cristabel.
>
>
>
> On 07/29/2011 04:45 PM, Jannis wrote:
>> Well,if you would have had a look at ?POSIXct the documentation  
>> would have given
>> you quite a comprehensive explanation of the meaning of the values  
>> of your time vector as they are the values these POSIXct values are  
>> actually stored in (they are seconds since 1970-01-01).  
>> Additionally you would have been redirected to as.POSIXct() which  
>> converts all sorts of objects to POSIXct. I would expect this  
>> function to return your desired format if you feed it with the  
>> numeric values that locator() returned.
>>
>>
>> HTH
>> Jannis
>>
>>
>>
>> On 07/29/2011 03:40 PM, cristabel.duran at waldbau.uni-freiburg.de  
>> wrote:
>>> Dear R-list,
>>>
>>> I have a plot with y-axis corresponding to wind measurments
>>> and x-axis with date-time information.
>>> When I want to identify some extrem wind events in the
>>> wind-curve, I use locator() to get the exact
>>> date-information, by clicking in the points in graph I?m
>>> interested in.
>>> I get in the R console the x and y coordinates.
>>> The x coordinates are not in a POSIXct format, I guess R is
>>> returning the x coordinates in a time unit as miliseconds
>>> or something else.
>>>
>>> Do anyone how to get the x coordinates directly in a
>>> POSIXct format?
>>>
>>> Thanks in advance!
>>> Cristabel.
>>>
>>>
>>> Cristabel Dur?n Rangel. PhD Student.
>>> Institute of Silviculture. Faculty of Forest and
>>> Environmental Sciences. University of Freiburg.
>>> Germany
>>> Telf: +49 (761) 203 8604 (ofc)
>>>
>>> ?Man lernt die Physiognomie einer Landschaft desto besser
>>> kennen, je genauer man die einzelnen Z?ge auffa?t, sie
>>> untereinander vergleicht und so auf dem Wege der Analysis
>>> den Quellen der Gen?sse nachgeht, die uns das gro?e
>>> Naturgem?lde bietet.?
>>>                Alexander von Humboldt, 1799
>>>
>>> ______________________________________________
>>> R-help at 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.
>>
>
> ______________________________________________
> R-help at 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, MD
West Hartford, CT

Thanks David and Janis,
now the result is logic!

have a nice WE,
Cristabel.


On 07/29/2011 06:32 PM, David Winsemius wrote:
>
> On Jul 29, 2011, at 12:21 PM, cristabel.duran wrote:
>
>> Hi Janis,
>> thank you for you answer.
>>
>> Actually already I did exactly what you said. However, when I convert 
>> the number of "seconds" from the first measurement (some day
in July
>> 2010) then a I get a date in the year 2050 which is impossible. The 
>> latest date possible is 29March2011.
>>
>> my value in ?seconds?: 1285038419
>> z <- 1285038419
>> as.POSIXct(z, origin="2010-07-15")
>> "2051-04-04 03:06:59 CEST"
>>
>> any clue why I get this date?
>
> Because the default origin is 1970-01-01
>
> > z <- 1285038419
> > as.POSIXct(z, origin="1970-01-01")
> [1] "2010-09-21 04:06:59 EDT"
>

I keep the following function handy so that I can change the numeric
value from POSIXct back to POSIXct; I tend to keep the numeric in
matrices since it allows faster operations in some cases.  This just
puts the appropriate classes on the object; quicker than using
as.POSIXct(z, origin="1970-01-01")

 unix2POSIXct <- function (time) structure(time, class =
c("POSIXt", "POSIXct"))
> z <- 1285038419
> as.POSIXct(z, origin="1970-01-01")
[1] "2010-09-21 04:06:59 EDT"
> unix2POSIXct(z)
[1] "2010-09-20 23:06:59 EDT"
>

On Fri, Jul 29, 2011 at 9:40 AM,
<cristabel.duran at waldbau.uni-freiburg.de>
wrote:
> Dear R-list,
>
> I have a plot with y-axis corresponding to wind measurments
> and x-axis with date-time information.
> When I want to identify some extrem wind events in the
> wind-curve, I use locator() to get the exact
> date-information, by clicking in the points in graph I?m
> interested in.
> I get in the R console the x and y coordinates.
> The x coordinates are not in a POSIXct format, I guess R is
> returning the x coordinates in a time unit as miliseconds
> or something else.
>
> Do anyone how to get the x coordinates directly in a
> POSIXct format?
>
> Thanks in advance!
> Cristabel.
>
>
> Cristabel Dur?n Rangel. PhD Student.
> Institute of Silviculture. Faculty of Forest and
> Environmental Sciences. University of Freiburg.
> Germany
> Telf: +49 (761) 203 8604 (ofc)
>
> ?Man lernt die Physiognomie einer Landschaft desto besser
> kennen, je genauer man die einzelnen Z?ge auffa?t, sie
> untereinander vergleicht und so auf dem Wege der Analysis
> den Quellen der Gen?sse nachgeht, die uns das gro?e
> Naturgem?lde bietet.?
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Alexander von Humboldt, 1799
>
> ______________________________________________
> R-help at 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.
>


-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?