[R] xyplot.zoo trouble with the index when I use microseconds (type POSIXct)
Laurent Rhelp
L@urentRHe|p @end|ng |rom |ree@|r
Mon Feb 22 21:20:36 CET 2021
yes, good idea, eventually here's what I will do:
time(DF.w) <- as.POSIXlt(time(DF.w))$sec
myticks <- round(pretty(time(DF.w)),6)
mylabels <- as.character(formatC(myticks,format =
"f",digits=6,width=9,flag=" "))
xyplot( DF.w
, xlab = paste0("Seconds from ",format(mystart,"%Y-%m-%d %H:%M"))
, type = "l"
, screens = 1
, col = c("red","blue","black")
, scales = list( y= list(relation = "free", abbreviate=TRUE)
, x = list( at = myticks, labels = mylabels
, rot = 45, abbreviate = FALSE
, cex = 0.6)
)
)
Thank you
Le 22/02/2021 à 19:32, Gabor Grothendieck a écrit :
> Also, it might be better to simply use seconds as the time. In that
> case both plot and xyplot run without error.
>
> time(DF.w) <- as.POSIXlt(time(DF.w))$sec
> # now run plot or xyplot as before
>
> On Mon, Feb 22, 2021 at 11:56 AM Gabor Grothendieck
> <ggrothendieck using gmail.com> wrote:
>> I assume that this is a lattice problem. Replacing xyplot with plot
>> and using all the same arguments there is no error.
>>
>>
>> On Mon, Feb 22, 2021 at 11:26 AM Laurent Rhelp <LaurentRHelp using free.fr> wrote:
>>> Dear R-Help-List,
>>>
>>> I have to process time series with a sampling frequency of 1 MHz.
>>> I use the POSIXct format for the date-times with microsecond in a zoo
>>> object and the xyplot.zoo function to do the graphs.
>>> As I show in the below example I had a trouble to plot the labels on the
>>> x-axis with an error message. I found a solution but I would like to
>>> know if I miss something.
>>> The link
>>> https://stackoverflow.com/questions/7726034/how-r-formats-posixct-with-fractional-seconds
>>>
>>> helped me to understand how to print the POSIXct value to see the
>>> microseconds thanks to the function myformat.POSIXct:
>>>
>>> myformat.POSIXct <- function(x, digits=6)
>>> {
>>> x2 <- round(unclass(x), digits)
>>> attributes(x2) <- attributes(x)
>>> x <- as.POSIXlt(x2,origin="1970-01-01",tz="GMT")
>>> x$sec <- round(x$sec, digits)
>>> format.POSIXlt(x, paste("%Y-%m-%d %H:%M:%OS",digits,sep=""),tz="GMT")
>>>
>>> }
>>>
>>>
>>> ## The example giving the error message:
>>>
>>> library(lattice)
>>> library(zoo)
>>>
>>> ##
>>> options(digits = 16) # to see all the digits on the screen
>>> options(digits.secs = 6) # to see the microseconds
>>> # mock data
>>> # a sine with a frequency f0 and two others with a delay
>>> Fs <- 1e+6 # sampling frequency 1 MHz
>>> Ts <- 1/Fs
>>> # frequency of the sinus
>>> f0 <- 100000
>>> t0 <- 1/f0
>>> time <- seq(0, length = 1000, by = Ts)
>>> A1 <- 1
>>> y1 <- A1 * sin(2*pi*f0*time)
>>> y2 <- 2 * A1 * sin(2*pi*f0*(time+0.000002))
>>> y3 <- 3 * A1 * sin(2*pi*f0*(time+0.000005))
>>> ## creation of a dataframe:
>>> ##
>>> DF <- data.frame( time = time, y1 = y1, y2 = y2, y3 = y3)
>>> # Since I want to allow for the datetime POSIXct format on the x-axis
>>> # for the plot I transform my dataframe in a zoo object
>>> #
>>> # say that my acquisition began at "2021-02-08 09:15:50.000000"
>>> #
>>> mystart <- as.POSIXct("2021-02-08 09:15:50.000000", format = "%Y-%m-%d
>>> %H:%M:%OS",tz="GMT")
>>> mystart
>>> # To see the correct datetime I use the myformat.POSIXct function
>>> myformat.POSIXct(mystart)
>>> ##
>>> ## using the method seq.POSIXct as following doesn't work:
>>> ## mydatetime <- seq( mystart , length = nrow(DF), by = "0.000001 sec")
>>> ## head( myformat.POSIXct(mydatetime) )
>>> ## if I use the following command it works:
>>> mydatetime <- seq( mystart , length = nrow(DF), by = 0.000001)
>>> head( myformat.POSIXct(mydatetime) )
>>> ## I do the zoo object:
>>> DF.z <- zoo(DF[,-1],order.by = mydatetime)
>>> ## We don't see the correct value for the index:
>>> head(DF.z)
>>> # time y1 y2 y3
>>> # 2021-02-08 09:15:50.000000 0e+00 0.000000000000000e+00
>>> 1.902113032590307e+00 3.673819061467132e-16
>>> # 2021-02-08 09:15:50.000000 1e-06 5.877852522924730e-01
>>> 1.902113032590307e+00 -1.763355756877419e+00
>>> # 2021-02-08 09:15:50.000001 2e-06 9.510565162951535e-01
>>> 1.175570504584947e+00 -2.853169548885460e+00
>>> # 2021-02-08 09:15:50.000003 3e-06 9.510565162951536e-01
>>> 1.133099690464601e-15 -2.853169548885460e+00
>>> # 2021-02-08 09:15:50.000004 4e-06 5.877852522924736e-01
>>> -1.175570504584946e+00 -1.763355756877420e+00
>>> # 2021-02-08 09:15:50.000005 5e-06 5.665498452323003e-16
>>> -1.902113032590306e+00 -3.399299071393802e-15
>>> # If I use myformat.POSIXct I see that the index is correct in the
>>> object DF:
>>> head(myformat.POSIXct(index(DF.z)))
>>> ## and when I plot I have an error:
>>> xyplot( DF.z
>>> , screens = c(1,1,1)
>>> , type = "l"
>>> , col = c("red","blue","black")
>>>
>>> )
>>>
>>> # Error in prettyDate_TMP(x, ...) : range too small for min.n
>>>
>>> # if I process by hand the plot of the labels on the x-axis it works:
>>> #
>>> myend <- tail(mydatetime,1)
>>>
>>> myticks <- seq( mystart , to = myend , length = 5)
>>> mylabels <- format(myticks,"%H:%M:%OS")
>>>
>>> xyplot( DF.z
>>> , screens = c(1,1,1)
>>> , type = "l"
>>> , col = c("red","blue","black")
>>> , scales = list(
>>> y= list(relation = "free", abbreviate=TRUE),
>>> x = list( at = myticks, labels = mylabels
>>> , rot = 45, cex = 0.5)
>>> )
>>> )
>>> # The microseconds are well taken into account with the window function
>>> # if I want to plot only 100 microseconds but there is of course the same
>>> # trouble for the plot
>>>
>>> myend <- as.POSIXct("2021-02-08 09:15:50.000100", format = "%Y-%m-%d
>>> %H:%M:%OS",tz="GMT")
>>> myformat.POSIXct(myend)
>>>
>>> DF.w <- window( DF.z ,start = mystart, end = myend)
>>>
>>> myticks <- seq( mystart , to = myend , length = 5)
>>> mylabels <- format(myticks,"%H:%M:%OS")
>>>
>>> xyplot( DF.w
>>> , screens = c(1,1,1)
>>> , type = "l"
>>> , col = c("red","blue","black")
>>> )
>>>
>>> ## Error in prettyDate_TMP(x, ...) : range too small for min.n
>>>
>>> xyplot( DF.w
>>> , screens = c(1,1,1)
>>> , type = "l"
>>> , col = c("red","blue","black")
>>> , scales = list(
>>> y= list(relation = "free", abbreviate=TRUE),
>>> x = list( at = myticks, labels = mylabels
>>> , rot = 45, cex = 0.5)
>>> )
>>> )
>>>
>>> May you please tell me if I miss something in the way to use POSIXct
>>> with microseconds in a zoo object ?
>>>
>>> Thank you
>>> Laurent
>>>
>>>
>>>
>>>
>>>
>>>
>>> --
>>> L'absence de virus dans ce courrier électronique a été vérifiée par le logiciel antivirus Avast.
>>> https://www.avast.com/antivirus
>>>
>>> ______________________________________________
>>> R-help using 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/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
>> --
>> Statistics & Software Consulting
>> GKX Group, GKX Associates Inc.
>> tel: 1-877-GKX-GROUP
>> email: ggrothendieck at gmail.com
>
>
--
L'absence de virus dans ce courrier électronique a été vérifiée par le logiciel antivirus Avast.
https://www.avast.com/antivirus
More information about the R-help
mailing list