[R] Adding lines to two graphs alternately

[Jim Lemon]

On 07/29/2010 07:02 AM, Dennis Fisher wrote:
> Colleagues
>
> I do a series of calculations, then add some output as a line in a graphic.  This is repeated a large number of times.  Then, I move to the next panel and do a similar set of calculations, add lines, ....
>
> Many of the calculations are identical for the two panels, so the calculations are done twice.  In order to avoid this redundancy, it would be ideal to do the following:
> 	1.  Set up the two panels (i.e., draw the axes for each
> 	2.  Do the calculations for the first iteration for both panels.  Draw the line in each panel.  Then move to the second iteration.
> In other words, I am trying to add to both two panels in an alternating manner -- do some calculations, add a line to panel 1, then add a line to panel 2, then do more calculations.
>
Hi Dennis,
You are probably looking for split.screen. You can specify the layout:

split.screen(c(1,2))

make a plot on each screen:
plot(1:5)
screen(2)
plot(5:1)

swap back and forth to add lines

screen(1,FALSE)
lines(c(2,5,4,3,1))
screen(2,FALSE)
lines(c(1,2,5,2,3))

and so on.

Jim