[R] Colouring a grid segment

Jim Lemon jim at bitwrit.com.au
Thu Oct 8 08:39:25 CEST 2009

On 10/08/2009 01:15 PM, darrenh65 wrote:
> Hi,
> I am attempting to create a polar chart (using plotrix polar.plt) and I need
> to colour a segment of the grid to indicate an area of interest, say from
> 90-120 degrees, for arguments sake. Is this possible? I can colour the whole
> grid by passing the grid.bg parameter through to radial.plot but I cannot
> find a way to colour a segment.
> thanks,
> Darren
Hi Darren,
You're right, there isn't any way to color just one sector of the 
background in a polar.plot. That's the bad news. The slightly less bad 
news is that I think you can kludge it by calling polar.plot twice with 
par(new=TRUE) between. First do the plot without the sector, noting the 
maximum extent of the grid ("maxlength" in the code). Then plot the 
polygon by calling the function so:


(you may want more than 40 points) Then plot your real data on top of 
this. I can't test this right now, but will try it out in the next day 
or so.


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