[R] How to plot dates

[Jeff Newmiller]

You don't seem to have a Y_Var in your data. What is it that you want to plot?

On March 16, 2021 9:21:05 AM PDT, Gregory Coats via R-help <r-help using r-project.org> wrote:
>Sarah, Thank you. Yes, now as.POSIXct works.
>But the ggplot command I was told to use yields an Error message, and
>there is no output plot.
>Please help me. Greg
>> library(ggplot2)
>> myDat <- read.table(text =
>+ "datetime
>+ 2021-03-11 10:00:00
>+ 2021-03-11 14:17:00
>+ 2021-03-12 05:16:46
>+ 2021-03-12 09:17:02
>+ 2021-03-12 13:31:43
>+ 2021-03-12 22:00:32
>+ 2021-03-13 09:21:43",
>+ sep = ",", header = TRUE)
>> head(myDat)
>             datetime
>1 2021-03-11 10:00:00
>2 2021-03-11 14:17:00
>3 2021-03-12 05:16:46
>4 2021-03-12 09:17:02
>5 2021-03-12 13:31:43
>6 2021-03-12 22:00:32
>> myDat$datetime <- as.POSIXct(myDat$datetime, tz = "", format
>="%Y-%M-%d %H:%M:%OS”)
>> ggplot(myDat, aes(x=datetime, y = Y_Var)) + geom_point()
>Error in FUN(X[[i]], ...) : object 'Y_Var' not found
>
>> On Mar 16, 2021, at 9:36 AM, Sarah Goslee <sarah.goslee using gmail.com>
>wrote:
>> 
>> Hi,
>> 
>> It doesn't have anything to do with having a Mac - you have POSIX.
>> 
>> It's because something is wrong with your data import. Looking at the
>> head() output you provided, it looks like your data file does NOT
>have
>> a header, because there's no datetime column, and the column name is
>> actually X2021.03.11.10.00.0
>> 
>> So you specified a nonexistent column, and got a zero-length answer.
>> 
>> With correct specification, the as.POSIXct function works as expected
>on Mac:
>> 
>> myDat <- read.table(text =
>> "datetime
>> 2021-03-11 10:00:00
>> 2021-03-11 14:17:00
>> 2021-03-12 05:16:46
>> 2021-03-12 09:17:02
>> 2021-03-12 13:31:43
>> 2021-03-12 22:00:32
>> 2021-03-13 09:21:43",
>> sep = ",", header = TRUE)
>> 
>> myDat$datetime <- as.POSIXct(myDat$datetime, tz = "", format =
>> "%Y-%M-%d %H:%M:%OS")
>> 
>> Sarah
>> 
>> On Tue, Mar 16, 2021 at 9:26 AM Gregory Coats via R-help
>> <r-help using r-project.org> wrote:
>>> 
>>> My computer is an Apple MacBook. I do not have POSIX.
>>> The command
>>> myDat$datetime <- as.POSIXct(myDat$datetime, tz = "", format =
>"%Y-%M-%d %H:%M:%OS")
>>> yields the error
>>> Error in `$<-.data.frame`(`*tmp*`, datetime, value = numeric(0)) :
>>>  replacement has 0 rows, data has 13
>>> Please advise, How to proceed?
>>> Greg Coats
>>> 
>>>> library(ggplot2)
>>>> # Read a txt file on the Desktop, named "myDat.txt"
>>>> myDat <- read.delim("~/Desktop/myDat.txt", header = TRUE, sep =
>",")
>>>> head(myDat)
>>>  X2021.03.11.10.00.00
>>> 1  2021-03-11 14:17:00
>>> 2  2021-03-12 05:16:46
>>> 3  2021-03-12 09:17:02
>>> 4  2021-03-12 13:31:43
>>> 5  2021-03-12 22:00:32
>>> 6  2021-03-13 09:21:43
>>>> # convert data to date time object
>>>> myDat$datetime <- as.POSIXct(myDat$datetime, tz = "", format =
>"%Y-%M-%d %H:%M:%OS")
>>> Error in `$<-.data.frame`(`*tmp*`, datetime, value = numeric(0)) :
>>>  replacement has 0 rows, data has 13
>>>> 
>>>        [[alternative HTML version deleted]]
>>> ______________________________________________
>>> 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.
>> -- 
>> Sarah Goslee (she/her)
>> http://www.numberwright.com
>
>
>	[[alternative HTML version deleted]]
>
>______________________________________________
>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.

-- 
Sent from my phone. Please excuse my brevity.