[R] Shaded areas in R

[Duncan Murdoch]

On 26/05/2016 5:37 AM, Óscar Jiménez wrote:
> Hello,
>
> I'm working with R language, and plotting some parameters over time. I need
> to draw a shaded area under the curve of eacj parameter.
>
> For that, I might use the polygon (x,y) function, assigning coordinates
> (x,y) to each vertex of my polygon. To do so, "x" and "y" must be vectors
> with numerical values, but since my x-axis is a time series, I cannot
> assing a numerical value to my "x" coordinate, because time variable is a
> "character" variable.
>
> Is there any option to use the function polygin (x,y) in this case, or any
> other function that allows me to draw a shaded area under the curve on a
> time series basis?

Times and dates just print like characters, they aren't actually 
characters.  For example,

  x <- Sys.Date() + 1:20
  y <- rnorm(20)
  plot(y ~ x)
  polygon(c(x, x[20], x[1]), c(y, 0, 0), col="gray")

Duncan Murdoch