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

[Jim Lemon]

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
>
>