[R] How to plot dates

[Gregory Coats]

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
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>> and provide commented, minimal, self-contained, reproducible code.
> -- 
> Sarah Goslee (she/her)
> http://www.numberwright.com


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