R help - Mar 2011 - Reference Lines Using Grid Graphics

Hi 

I would like to be able to add reference lines to a series of plots that are
built using the Grid graphics package. These lines should coincide with tick
marks which are different on each plot.

I can add the lines manually using the grid.lines() function but would like
to understand how to generate them on the fly.

Any help would be gratefully received.

Kind regards

Pete


#######################################################################
# FUNCTION MYPLOT
#######################################################################
myplot=function(i,j){
 pushViewport(viewport(layout.pos.col=i,layout.pos.row=j)) 
 pushViewport(plotViewport(c(3,2,2,3)))

 x <- runif(10)
 y <- (i+j)*runif(10)

 pushViewport(dataViewport(range(x),pretty(y),name="plotRegion"))
 
 grid.points(x, y)
 grid.rect()
 grid.xaxis()
 grid.yaxis(main=FALSE)
  
 # How can I use grid.lines to create reference lines at the tick marks for
each graph?
 # grid.lines(x=0:1,y=0.2) 

 grid.text(paste("Plot ",i," ",j,sep=""), y =
unit(1, "npc") + unit(0.5,
"lines"),  gp = gpar(fontsize = 16))
 popViewport()
 popViewport(2)
}
#######################################################################
# END FUNCTION MYPLOT
#######################################################################


grid.newpage()
grid.rect(gp=gpar(fill="white"))
pushViewport(viewport(layout=grid.layout(2, 2)))
myplot(1,1)
myplot(1,2)
myplot(2,1)
myplot(2,2)
popViewport()

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Apologies ....

I forgot to include that the reference lines should be for the y axis only.

Thanks.

Pete

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On Fri, Mar 11, 2011 at 4:50 PM, Pete Brecknock <Peter.Brecknock at
bp.com> wrote:
> Hi
>
> I would like to be able to add reference lines to a series of plots that
are
> built using the Grid graphics package. These lines should coincide with
tick
> marks which are different on each plot.
>
> I can add the lines manually using the grid.lines() function but would like
> to understand how to generate them on the fly.
>
> Any help would be gratefully received.
>
> Kind regards
>
> Pete
>
>
> #######################################################################
> # FUNCTION MYPLOT
> #######################################################################
> myplot=function(i,j){
> ?pushViewport(viewport(layout.pos.col=i,layout.pos.row=j))
> ?pushViewport(plotViewport(c(3,2,2,3)))
>
> ?x <- runif(10)
> ?y <- (i+j)*runif(10)
>
> ?pushViewport(dataViewport(range(x),pretty(y),name="plotRegion"))
>
> ?grid.points(x, y)
> ?grid.rect()
> ?grid.xaxis()
> ?grid.yaxis(main=FALSE)
>
> ?# How can I use grid.lines to create reference lines at the tick marks for
> each graph?
> ?# grid.lines(x=0:1,y=0.2)
>
> ?grid.text(paste("Plot ",i," ",j,sep=""), y =
unit(1, "npc") + unit(0.5,
> "lines"), ?gp = gpar(fontsize = 16))
> ?popViewport()
> ?popViewport(2)
> }
> #######################################################################
> # END FUNCTION MYPLOT
> #######################################################################
>
>
> grid.newpage()
> grid.rect(gp=gpar(fill="white"))
> pushViewport(viewport(layout=grid.layout(2, 2)))
> myplot(1,1)
> myplot(1,2)
> myplot(2,1)
> myplot(2,2)
> popViewport()
>
Try this:

 for(yy in pretty(y)) grid.lines(0:1, unit(yy, "native"))


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GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com

Thanks Gabor. I owe you again.

Kind regards

Pete

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