R help - May 2011 - Converting the graphics window to a data matrix

I'm wondering if anyone is aware of a way to take what is visible in the
R graphics window, pixelate it, and express that pixellation in a
numeric matrix. For example, I am using the following command to create
a  black (present) and white (absent) spatial simulation of grass
tussock distribution.
>
symbols(x=runif(100,-.5,1.5),y=runif(100,-.5,1.5),circles=runif(100)/30,
inches=F,bg=1,xlim=c(0,1),ylim=c(0,1))

What I would like to end up with is a 2 dimensional matrix that
indicates presence/absence of grass in any given pixel as per the image
generated from the above graphics plot. 

Thanks

Terry Beutel




********************************DISCLAIMER**************...{{dropped:15}}

On Thu, May 19, 2011 at 5:19 AM, Beutel, Terry S
<Terry.Beutel at deedi.qld.gov.au> wrote:
> I'm wondering if anyone is aware of a way to take what is visible in
the
> R graphics window, pixelate it, and express that pixellation in a
> numeric matrix. For example, I am using the following command to create
> a ?black (present) and white (absent) spatial simulation of grass
> tussock distribution.
>
>>
> symbols(x=runif(100,-.5,1.5),y=runif(100,-.5,1.5),circles=runif(100)/30,
> inches=F,bg=1,xlim=c(0,1),ylim=c(0,1))
>
> What I would like to end up with is a 2 dimensional matrix that
> indicates presence/absence of grass in any given pixel as per the image
> generated from the above graphics plot.
 Instead of drawing to the screen, you can use the 'png' function to
create a graphics device that "draws" to an image file. Then you can
read that image file into R and get it as a matrix.

 You probably also want to set some of the margin and axis parameters
so the plotting region fills the whole device, and you dont have the
axes and tick marks etc confusing the matrix.

 That's some pointers for starters. I've not had breakfast yet...

Barry

See

library(grid)

?grid.cap

and this page for background:
http://developer.r-project.org/Raster/raster-RFC.html



On Thu, May 19, 2011 at 2:19 PM, Beutel, Terry S <
Terry.Beutel@deedi.qld.gov.au> wrote:
> I'm wondering if anyone is aware of a way to take what is visible in
the
> R graphics window, pixelate it, and express that pixellation in a
> numeric matrix. For example, I am using the following command to create
> a  black (present) and white (absent) spatial simulation of grass
> tussock distribution.
>
> >
> symbols(x=runif(100,-.5,1.5),y=runif(100,-.5,1.5),circles=runif(100)/30,
> inches=F,bg=1,xlim=c(0,1),ylim=c(0,1))
>
> What I would like to end up with is a 2 dimensional matrix that
> indicates presence/absence of grass in any given pixel as per the image
> generated from the above graphics plot.
>
> Thanks
>
> Terry Beutel
>
>
>
>
> ********************************DISCLAIMER**************...{{dropped:15}}
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Michael Sumner
Institute for Marine and Antarctic Studies, University of Tasmania
Hobart, Australia
e-mail: mdsumner@gmail.com

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