Re: [R] identify() - image()

About this list Date view Thread view Subject view Author view Attachment view

From: javier garcia - CEBAS (rn001@cebas.csic.es)
Date: Fri 28 May 2004 - 04:59:20 EST


Message-id: <200405271858.i4RIwhp13329@natura.cebas.csic.es>

Thanks Barry (and Thomas),

I wanted it to extract information from imported maps from the GIS GRASS,
with a few modifications the functions works also very well for this.

Best regards,

Javier
-----------
El Mié 26 May 2004 19:40, Barry Rowlingson escribió:
> javier garcia - CEBAS wrote:
> > Hi all;
> > Just to ask if you know about any available function in R to identify
> > points in a image plotted in X11. Something like the function identify(),
> > but able to extract (x,y,value) groups from the image.
>
> this is what I use:
>
> image.identify <- function(xyz, mark=T, digits=3){
>
> nx <- length(xyz$x) - 1
> ny <- length(xyz$y) - 1
> if(!all(dim(xyz$z)==c(nx,ny))){
> stop("Really need image specified by cell edges")
> }
> res <- data.frame()
> xy <- locator(1)
> while(!is.null(xy)){
> xbin <- as.numeric(cut(xy$x,xyz$x))
> ybin <- as.numeric(cut(xy$y,xyz$y))
> if(mark){
> points(xy$x,xy$y,pch=19,cex=.5,col="blue")
>
> text(xy$x,xy$y,format(xyz$z[xbin,ybin],digits=digits),adj=-.2,col="blue")
> }
> cat("[",xbin,",",ybin,"] = ",xyz$z[xbin,ybin],"\n",sep='')
> res <-
> rbind(res,data.frame(i=xbin,j=ybin,x=xy$x,y=xy$y,z=xyz$z[xbin,ybin]))
> xy <- locator(1)
> }
> res
> }
>
> Try:
> > m=list(x=1:11,y=1:11,z=matrix(runif(100),10,10))
> > image(m)
> > identify.image(m)
>
> then click some things. Button 2 to finish.
>
> The returned data frame gives row and column in the 'z' matrix, x and
> y coordinates, and value of the z matrix at that point.
>
> Baz

______________________________________________
R-help@stat.math.ethz.ch mailing list
https://www.stat.math.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html


About this list Date view Thread view Subject view Author view Attachment view

This archive was generated by hypermail 2.1.3 : Mon 31 May 2004 - 23:05:13 EST