[R] Converting the graphics window to a data matrix

[Greg Snow]

The EBImage package from bioconductor will read image files (png and others), the object read has a slot called .Data that is a 3 dimensional array with one dimension being the color (red,green,blue), so you could just grab one of those 3 layers and it would probably be what you want (or some function of that layer, or combination of the 3 layers).

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Beutel, Terry S
> Sent: Thursday, May 19, 2011 10:02 PM
> To: Barry Rowlingson
> Cc: r-help at r-project.org
> Subject: Re: [R] Converting the graphics window to a data matrix
> 
> Thanks Barry. I have now got as far as creating the png (or gif or
> tiff) images (as per your suggestions). But I am unable to work out how
> to convert each to a 2 dimensionional numeric matrix showing the
> spatial distribution of occupied/unoccupied pixels in R. Any
> suggestions anybody?
> Thanks
> 
> Terry
> 
> -----Original Message-----
> From: b.rowlingson at googlemail.com [mailto:b.rowlingson at googlemail.com]
> On Behalf Of Barry Rowlingson
> Sent: Thursday, 19 May 2011 4:19 PM
> To: Beutel, Terry S
> Cc: r-help at r-project.org
> Subject: Re: [R] Converting the graphics window to a data matrix
> 
> 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)/3
> > 0,
> > 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
> 
> 
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