[datatable-help] IDateTime and plotting thereof
Steven C. Bagley
steven.bagley at gmail.com
Sat Dec 17 04:51:19 CET 2011
Farrel,
Here's a slightly simpler way. Using the data from your example:
qplot(idate, as.POSIXct(itime, tz=""), data=dtdt, xlab="Date", ylab="Time")
The data in idate (of class IDate) can be converted by ggplot2. However, ggplot2 doesn't know anything about ITime, which is just an integer offset from midnight, so you have to call as.POSIXct yourself. If you don't pass in the timezone argument, then everything is done in UTC and times wrap around into the wrong day. Note also the order of arguments to qplot and the use of column names from the data.table passed as the data argument, which is the preferred ggplot2 style, although certainly not required.
I hope this helps.
--Steve
On Dec 16, 2011, at 9:02 AM, Farrel Buchinsky wrote:
> I discovered that if I wanted control of the dates on the x axis I had to convert the IDate to as.POSIXct as well otherwise strange and undesirable things started happening - for instance all the dates were the same if I tried to format the dates in a particular way. So here is what I finished with my original data set.
>
> qplot(data=ape.ph,x=as.POSIXct(date,tz="EST"), y=as.POSIXct(timei,tz="EST")) +
> scale_y_datetime(name="time",format="%H:%M") +
> scale_x_datetime(name="November",major="1 day", format = "%a %d")
>
> Farrel Buchinsky
> Google Voice Tel: (412) 567-7870
>
>
>
> On Fri, Dec 16, 2011 at 10:35, Farrel Buchinsky <fjbuch at gmail.com> wrote:
> Dear Matthew
>
> Thank you very much for your help.
> I found something fascinating. I do not know the details of POSIXct and iTime but look at this.
>
> library(data.table)
> library(ggplot2)
>
> datetimes <- c("2011 NOV18 09:29:16", "2011 NOV18 10:42:40", "2011 NOV18 10:47:12",
> "2011 NOV18 11:06:01", "2011 NOV18 11:35:34", "2011 NOV18 11:51:09",
> "2011 NOV18 12:23:16", "2011 NOV18 12:30:01", "2011 NOV18 12:34:28",
> "2011 NOV18 12:51:45", "2011 NOV18 12:56:37", "2011 NOV18 13:28:17",
> "2011 NOV18 13:37:41", "2011 NOV18 13:49:07", "2011 NOV18 14:47:04",
> "2011 NOV18 15:16:39", "2011 NOV18 15:17:10", "2011 NOV18 15:19:19",
> "2011 NOV19 08:28:00", "2011 NOV19 09:20:55", "2011 NOV19 10:41:25",
> "2011 NOV19 10:41:41", "2011 NOV19 12:53:15", "2011 NOV20 11:22:59",
> "2011 NOV20 19:53:25", "2011 NOV21 07:16:35", "2011 NOV21 08:50:45",
> "2011 NOV21 09:32:59", "2011 NOV21 09:43:01", "2011 NOV21 10:29:52",
> "2011 NOV21 10:34:23", "2011 NOV21 10:37:09", "2011 NOV21 10:55:18",
> "2011 NOV21 11:43:46", "2011 NOV21 11:46:50", "2011 NOV21 12:10:16",
> "2011 NOV21 12:16:44", "2011 NOV21 13:53:42", "2011 NOV21 13:53:43",
> "2011 NOV21 14:06:06", "2011 NOV21 14:23:39", "2011 NOV21 15:14:21",
> "2011 NOV21 15:35:53", "2011 NOV21 15:46:29", "2011 NOV21 15:49:37",
> "2011 NOV21 16:45:32", "2011 NOV21 20:36:31", "2011 NOV22 08:56:03",
> "2011 NOV22 09:33:12", "2011 NOV22 09:39:52", "2011 NOV22 10:40:46",
> "2011 NOV22 11:19:48", "2011 NOV22 11:23:32", "2011 NOV22 12:04:16",
> "2011 NOV22 12:07:04", "2011 NOV22 12:23:31", "2011 NOV22 12:28:54",
> "2011 NOV22 12:31:14", "2011 NOV22 12:53:31", "2011 NOV22 12:54:11",
> "2011 NOV22 13:41:54", "2011 NOV22 15:34:11", "2011 NOV23 07:03:44",
> "2011 NOV23 07:04:57", "2011 NOV23 08:01:42", "2011 NOV23 08:37:14",
> "2011 NOV23 08:57:55", "2011 NOV23 09:00:34", "2011 NOV23 09:10:38",
> "2011 NOV23 09:21:19", "2011 NOV23 09:23:58", "2011 NOV23 10:48:10",
> "2011 NOV23 11:23:58", "2011 NOV23 11:49:14", "2011 NOV23 12:19:44",
> "2011 NOV23 12:31:34", "2011 NOV23 12:48:00", "2011 NOV23 13:22:08",
> "2011 NOV23 13:30:36", "2011 NOV23 14:01:56", "2011 NOV23 14:38:15",
> "2011 NOV23 14:54:02", "2011 NOV23 15:33:31", "2011 NOV23 15:49:12",
> "2011 NOV25 09:21:42", "2011 NOV25 09:22:25", "2011 NOV25 09:24:22",
> "2011 NOV25 10:07:42", "2011 NOV25 15:03:15", "2011 NOV28 08:12:32",
> "2011 NOV28 09:20:39", "2011 NOV28 09:26:09", "2011 NOV28 10:25:47",
> "2011 NOV28 11:19:40", "2011 NOV28 11:54:54", "2011 NOV28 14:33:53",
> "2011 NOV28 15:08:25", "2011 NOV28 15:09:25", "2011 NOV28 15:23:07",
> "2011 NOV28 15:23:30", "2011 NOV28 15:50:35", "2011 NOV29 08:22:39",
> "2011 NOV29 09:08:51", "2011 NOV29 09:10:15", "2011 NOV29 10:44:17",
> "2011 NOV29 11:32:05", "2011 NOV29 12:00:52", "2011 NOV29 12:32:48",
> "2011 NOV29 13:21:50", "2011 NOV29 13:22:12", "2011 NOV29 13:22:38",
> "2011 NOV29 13:23:35", "2011 NOV29 13:28:38", "2011 NOV29 13:29:44",
> "2011 NOV29 13:30:25", "2011 NOV29 13:32:13", "2011 NOV29 13:33:28",
> "2011 NOV29 13:35:59", "2011 NOV29 13:37:01", "2011 NOV29 13:39:37",
> "2011 NOV29 13:41:33", "2011 NOV29 14:08:07", "2011 NOV29 14:09:53",
> "2011 NOV29 14:13:15", "2011 NOV29 14:16:16", "2011 NOV29 14:17:32",
> "2011 NOV29 14:37:05", "2011 NOV29 14:59:51", "2011 NOV29 14:59:51",
> "2011 NOV29 14:59:54", "2011 NOV29 15:00:10", "2011 NOV29 15:13:22",
> "2011 NOV29 16:09:50", "2011 NOV29 16:10:17", "2011 NOV29 16:31:14",
> "2011 NOV29 16:43:20", "2011 NOV30 09:22:09", "2011 NOV30 10:19:21",
> "2011 NOV30 11:42:04", "2011 NOV30 11:50:11", "2011 NOV30 12:21:11",
> "2011 NOV30 13:06:39")
>
> datetimes <- strptime(datetimes,"%Y %b%d %H:%M:%S")
> dtdt <- IDateTime(datetimes)
> setkey(x=dtdt,idate,itime)
> plot(dtdt$idate,dtdt$itime)#works although I still need to figure out how to get times that I, as a human, understand
> qplot(x=dtdt$idate,y=dtdt$itime) # gives an error
>
> #Error in as.data.frame.default(x[[i]], optional = TRUE) :
> # cannot coerce class '"ITime"' into a data.frame
>
> dtdt[,qplot(idate,itime)]#same error
>
>
> qplot(x=dtdt$idate,y=as.POSIXct(dtdt$itime,tz="EST")) #have to specify the time zone otherwise I got evertying at UTC
>
> Clearly this has something to do with the way ggplot wants its data. Plot handled it but qplot did not.
>
>
> Farrel Buchinsky<517.gif>
>
>
>
>
> On Fri, Dec 16, 2011 at 03:50, Matthew Dowle <mdowle at mdowle.plus.com> wrote:
> Hi.
>
> You should be able to add more than one column in one step using := by
> setting with=FALSE like this :
>
> > DT = data.table(a=1:3,b=4:6)
> > DT
> a b
> [1,] 1 4
> [2,] 2 5
> [3,] 3 6
> > DT[,c("newcol1","newcol2"):=list(7:9,3.14)]
> Error in `[.data.table`(DT, , `:=`(c("newcol1", "newcol2"),
> list(7:9, :
> LHS of := must be a single column name, when with=TRUE. When
> with=FALSE the LHS may be a vector of column names or positions.
>
> so set with=FALSE :
>
> > DT[,c("newcol1","newcol2"):=list(7:9,3.14),with=FALSE]
> Error in `[.data.table`(DT, , `:=`(c("newcol1", "newcol2"),
> list(7:9, :
> Logical error. Can only add new columns one at a time currently
> >
>
> I intended that to work so I'll take a look. But, the intention is at
> some point to enable this :
>
> DT[,{ newcol1 := ....
> newcol2 := ....
> newcol3 := newcol1 + newcol2
> }, by=... ]
>
> where not only can you add multiple columns by reference and by group,
> but they can 'see' previous columns just added. That's going to be quite
> tricky to implement so don't hold your breath!
>
> In the meantime it's either one at a time with :=, or use (slower) [<-
> method to add multiple columns (via at least one full table copy).
>
> Re plotting, I'm hoping to learn ggplot2 myself soon, so bear that in
> mind, but this is the way I thought should work :
>
> ape.ph[,qplot(date, timei)]
>
> If that gives the same error I'm not sure why it would try to coerce
> ITime into a data.frame. Does anyone else know? If you can provide some
> example data it might help save us time to reproduce it.
>
> Matthew
>
>
>
> On Thu, 2011-12-15 at 19:25 -0500, Farrel Buchinsky wrote:
> > I was able to take a column of dates and times that looked like this
> >
> > 2011 NOV18 09:29:16
> >
> >
> > I then tried this
> >
> > ape.ph[,date:=IDateTime(strptime(ape.ph$time,"%Y %b%d %H:%M:%S"))[[1]]]
> > ape.ph[,timei:=as.ITime(strptime(ape.ph$time,"%Y %b%d %H:%M:%S"))]
> >
> >
> > I had to create one column called date to accept the first column of
> > the IDateTime output. There does not appear to be a way to use the
> > IDateTime function and take both of its columns and stick it into the
> > data.table since one can only add one new column at a time as far as I
> > can tell. Anyway, I then created a variable timei to accept the time.
> >
> >
> > I wanted to plot the times that something happened on the y axis and
> > then on the x axis I wanted to have the various dates
> >
> >
> > library(ggplot2)
> > qplot(ape.ph[,date], ape.ph[,timei])
> >
> >
> > but alas I got this
> >
> >
> > Error in as.data.frame.default(x[[i]], optional = TRUE) :
> > cannot coerce class '"ITime"' into a data.frame
> >
> >
> > I am eventually hoping for this
> > qplot(ape.ph[,date], ape.ph[,timei]) +
> > scale_y_datetime(format="%H:%M:%S") +
> > xlab("Day") + ylab("Hour")
> >
> >
> > Do you have any examples of dates and times used in a data.table and
> > then being used to plot graphs? I would love to see some examples. I
> > could not find any
> >
> >
> >
> >
> > Farrel Buchinsky
> > Google Voice Tel: (412) 567-7870
> >
> >
> > _______________________________________________
> > datatable-help mailing list
> > datatable-help at lists.r-forge.r-project.org
> > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
>
>
>
>
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