[R] how to you use plot to plot multiple time series in one final graph

[Paul Murrell]

Hi


> |
> |
> | =========================== A
> |
> |
> |
> |
> | *************************** B
> |
> -----------------------------
> DIAGRAM 1
>
> in this contrived example there are two
> series A,B plotted against time. (x axis
> is time)
>
> problem: if the range for A and B are
> quite different R goes stupid and only
> shows either A or B but not both (depending
> on what plot command came last i think).
>
> how do you fix that?
>
> i played around with all sorts of things
> on plot including this last stab:
>
> plot.new()
> A <- c(...)
> B <- c(...)
> plot(a,axes=FALSE,ann=FALSE)
> plot(b,axes=FALSE,ann=FALSE)
> # using code NOT shown here I figure out the
> # min, maxes for the X axis and therefore
> # determine the right at and lab arguments
> # for axis
> axis(1,at...)
> axis(2,at...) # ditto for Y
>
> I can routinely get R to do a nice job with the
> X axis with above code BUT not Y. in the axis(2...)
> command the graphics line for the Y axis in the
> plot window goes DOWN beneath the X axis even
> though all Y lables are positive.
>
> R is too smart to be this crazy? what is my pilot
> error?


It *sounds* like you need xlim and ylim.  Does this silly example do the
sort of thing you want ... ?

    Ax <- sort(runif(100, 1, 200))
    Ay <- runif(100, 1, 200)
    Bx <- sort(runif(10, 1, 1000))
    By <- runif(10, 1, 1000)
    plot(Ax, Ay, xlim=range(Ax, Bx), ylim=range(Ay, By), type="l")
    lines(Bx, By, lty="dashed")


> i hesitate to ask (and this is NOT my burning
> question) but what would happen if A and B had
> different units. can you make R plot A against the
> left hand side Y axis and B against the right
> hand side axis with appropriately labled and ticked?


Yes;  horrible example that hopefully shows the idea ...

    plot(1:10)
    par(usr=c(par("usr")[1:2], 0, 1000))
    points(seq(1000, 1, length=10), pch=16)
    axis(4)

Hope that helps.

Paul


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