[R] Plotting zoo objects with chron axis

[Manta]

Dear all,

I have a problem which I'm not to fix. I have the following two series:

a=structure(c(33242.5196150509, 34905.8434338503, 38490.6957848689, 
38747.0287172129, 38919.1028597142, 39026.3956586941, 38705.5344288997, 
38545.6274379387, 38651.2079354205, 38748.2769580121), index =
structure(c(14029, 
14032, 14033, 14034, 14035, 14036, 14039, 14040, 14041, 14042
), class = Date), class = zoo)

b=structure(c(53337.7643740991, 52210.2079727035, 50235.4480363949, 
50667.1147389469, 50796.5403152116, 51113.5420947436, 51003.3603311344, 
50654.0539778796, 49927.5267060329, 49320.1813921822), index =
structure(c(14029, 
14032, 14033, 14034, 14035, 14036, 14039, 14040, 14041, 14042
), class = Date), class = zoo)

I want to plot them on the same chart, with the x-axis the Date, and the
y-axis the time in format %H:%M. At the moment, the y series is expressed in
seconds from midnight. I am confused with the as.POSIXct conversion.

 hours(min(rollrep))
[1] 9
 minutes(min(rollrep))
[1] 34
 seconds(min(rollrep))
[1] 27

however, by doing the following it seems the minimum time is 11:09, which is
not true.

as.POSIXct(round(min(rollrep)),origin=Sys.Date())
[1] 2013-08-09 11:09:14 CEST

Do you have any advice? Is there a way to plot only the hours and minutes,
without having to go to the Sys.Date?

Thank you,
Marco



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Re: [R] Plotting zoo objects with chron axis

[Enrico Schumann]

On Fri, 09 Aug 2013, Manta mantin...@libero.it writes:

 Dear all,

 I have a problem which I'm not to fix. I have the following two series:

 a=structure(c(33242.5196150509, 34905.8434338503, 38490.6957848689, 
 38747.0287172129, 38919.1028597142, 39026.3956586941, 38705.5344288997, 
 38545.6274379387, 38651.2079354205, 38748.2769580121), index =
 structure(c(14029, 
 14032, 14033, 14034, 14035, 14036, 14039, 14040, 14041, 14042
 ), class = Date), class = zoo)

 b=structure(c(53337.7643740991, 52210.2079727035, 50235.4480363949, 
 50667.1147389469, 50796.5403152116, 51113.5420947436, 51003.3603311344, 
 50654.0539778796, 49927.5267060329, 49320.1813921822), index =
 structure(c(14029, 
 14032, 14033, 14034, 14035, 14036, 14039, 14040, 14041, 14042
 ), class = Date), class = zoo)

 I want to plot them on the same chart, with the x-axis the Date, and the
 y-axis the time in format %H:%M. At the moment, the y series is expressed in
 seconds from midnight. I am confused with the as.POSIXct conversion.

 hours(min(rollrep))
 [1] 9
 minutes(min(rollrep))
 [1] 34
 seconds(min(rollrep))
 [1] 27

 however, by doing the following it seems the minimum time is 11:09, which is
 not true.

 as.POSIXct(round(min(rollrep)),origin=Sys.Date())
 [1] 2013-08-09 11:09:14 CEST

 Do you have any advice? Is there a way to plot only the hours and minutes,
 without having to go to the Sys.Date?

 Thank you,
 Marco

Please provide a *reproducible* example.  (What is 'rollrep'?  'Seconds
from midnight' may be ambiguous when there was a change to/from
summertime or when time zones are relevant.)

Perhaps something like this:

  require(zoo)
  plot(merge(a, b), plot.type = single, yaxt = n)
  midnight - ISOdatetime(2013, 1, 1, 0, 0, 0, GMT)
  sq - seq(0, 86400, by = 300)
  axis(2, at = sq, labels = format(midnight + sq, %H:%M))


-- 
Enrico Schumann
Lucerne, Switzerland
http://enricoschumann.net

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and provide commented, minimal, self-contained, reproducible code.