[R] How to specify year-month-day for a plot

Gregory Coats gregco@t@ @end|ng |rom me@com
Wed Dec 16 18:32:28 CET 2020

Jim, Thank you!
The data set begins
gcdf<-read.table(text="2013-12-29 19.175
2014-01-20 10.072
2014-02-12 10.241
I note that data begins in 2013. But the plot command does not show this first entry in 2013, and instead shows the second data pair as the first data pair. As a consequence, plot does not show the first data pair for 2013, and begins in 2014.

> On Dec 16, 2020, at 1:08 AM, Jim Lemon <drjimlemon using gmail.com> wrote:
> Hi Greg,
> I think this does what you want:
> gcdf$date<-as.Date(gcdf$date,"%Y-%m-%d")
> grid_dates<-as.Date(paste(2014:2020,1,1,sep="-"),"%Y-%m-%d")
> plot(gcdf$date, gcdf$gallons, main="2014 Toyota 4Runner", xlab="Date",
> ylab="Gallons",type="l",col="blue",yaxt="n")
> abline(h=seq(4,20,by=2),lty=4)
> abline(v=grid_dates,lty=4)
> axis(side=2,at=seq(4,20,by=2))
> Jim
> On Wed, Dec 16, 2020 at 2:16 PM Gregory Coats <gregcoats using me.com> wrote:
>> Jim, Thanks for your help with R.
>> Feeding into R the file R_plot_18.r yields for me, on my Mac, R_plot_18.pdf. Success.
>> I used abline to draw a horizontal background grid, and then used axis label to identify the values represented by the horizontal dashed background lines.
>> abline (h=c(2,4,6,8,10,12,14,16,18,20,22,24), lty=4, lwd=1.0, col="grey60")
>> Similarly, I would like to draw a dashed vertical background grid. But it is unclear to me how to direct R to draw a vertical dashed background grid because I am again baffled how to specify to R a date value such as 2018-10-20 @18:00. I welcome your guidance.
>> Greg
>> On Dec 13, 2020, at 10:58 PM, Jim Lemon <drjimlemon using gmail.com> wrote:
>> Hi Gregory,
>> On Mon, Dec 14, 2020 at 12:34 PM Gregory Coats <gregcoats using me.com> wrote:
>> ...
>> Is there a convenient way to tell R to interpret “2020-12-13” as a date?
>> Notice the as.Date command in the code I sent to you. this converts a
>> string to a date with a resolution of one day. If you want a higher
>> time resolution, use strptime or one of the other POSIX date
>> conversion functions.
>> Jim

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