Paul, Thanks very much! Your example code below shows exactly how to do what I wanted.
-Ben p.s., For the record, transRight <- current.transform() after the second call to pushViewport() seems to have gotten deleted from you example code below, but that was obvious. > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > On Behalf Of Paul Murrell > Sent: Monday, June 02, 2008 10:05 PM > To: Wittner, Ben, Ph.D. > Cc: [EMAIL PROTECTED] > Subject: Re: [R] transforming output of grid.locator() to coordinates of a > leaf viewport > > Hi > > > Wittner, Ben, Ph.D. wrote: > > Hadley, In my application the leaf viewports will not overlap, but I > guess that > > would not necessarily be the case for all applications. In any event, do > you > > happen to know how to transform coordinates in the top-level viewport to > > coordinates in another viewport in the tree? Thanks. -Ben > > > current.transform() transforms from *inches* within the current viewport > to *inches* on the overall device. Sounds like you need the inverse > transform. > > If you are in a position to be able to enumerate all of your leaf > viewports, then this may be a possible approach: > > - for each leaf viewport, visit the viewport and record the > current.transform() for each leaf viewport. Also record the size of the > current viewport (in inches). > - capture a click on the device (current viewport should be ROOT) in > *inches*, then iterate through the leaf viewports to determine which one > was clicked in. > - to determine whether the click was within the viewport, use something > like the following function (and check whether both new locations are > positive and smaller than the size of the viewport (in inches)): > > newloc <- function(loc, trans) { > temploc <- c(loc, 1) %*% trans > (temploc/temploc[3])[-3] > } > > Here's a simple example: > > # two "leaf" viewports > # (one on the left half of the device, one on the right) > grid.newpage() > pushViewport(viewport(x=0, width=.5, just="left", name="left")) > transLeft <- current.transform() > sizeLeft <- c(convertWidth(unit(1, "npc"), "inches", valueOnly=TRUE), > convertHeight(unit(1, "npc"), "inches", valueOnly=TRUE)) > # Draw a rect for visual reference > grid.rect(gp=gpar(fill=hcl(240, 60, 80))) > upViewport() > pushViewport(viewport(x=.5, width=.5, just="left", name="right")) > sizeRight <- c(convertWidth(unit(1, "npc"), "inches", valueOnly=TRUE), > convertHeight(unit(1, "npc"), "inches", valueOnly=TRUE)) > heightRight <- convertHeight(unit(1, "npc"), "inches", valueOnly=TRUE) > grid.rect(gp=gpar(fill=hcl(120, 60, 80))) > upViewport() > > # Get a click > # (current viewport is the ROOT viewport) > click <- grid.locator(unit="inches") > > # For each leaf viewport, calculate where the click was > leftClick <- newloc(unlist(click), solve(transLeft)) > rightClick <- newloc(unlist(click), solve(transRight)) > > # Which one was it in ? > all(leftClick > 0 & leftClick < sizeLeft) > all(rightClick > 0 & rightClick < sizeRight) > > > Does that help ? > > Paul > > > > > ________________________________ > > > > From: hadley wickham [mailto:[EMAIL PROTECTED] > > Sent: Sun 6/1/2008 3:24 PM > > To: Wittner, Ben, Ph.D. > > Cc: [EMAIL PROTECTED] > > Subject: Re: [R] transforming output of grid.locator() to coordinates of > a leaf > > viewport > > > > > > > > Ben, > > > > What if the click occurs over multiple viewports? > > > > Hadley > > > > On Mon, Jun 2, 2008 at 6:50 AM, Wittner, Ben, Ph.D. > > <[EMAIL PROTECTED]> wrote: > >> Short form: > >> > >> How do I transform the output of grid.locator() (or > >> grid.locator(unit='npc')) to the native (or npc) coordinates of a > viewport > > other > >> than the top-level viewport? > >> > >> Thanks in advance. -Ben > >> > >> Long form: > >> > >> I would like the user to be able to click anywhere on > the R > >> graphics window. I would then like to figure out which leaf viewport > the user > >> clicked in and compute the native coordinates in that leaf viewport of > the > >> user's click. > >> > >> I saw a 2005 response by Paul Murrell to a post by Gabor > >> Grothendieck roughly on this topic in which Paul suggested looking at > >> trellis.focus(). I've looked at trellis.focus() and > trellis.clickFocus(), but > >> they don't appear to do what I want in that a) it would appear that my > user > >> would have to click twice, once to specify which leaf viewport and then > again > > to > >> specify which point in that viewport and b) trellis.clickFocus() > appears to > > use > >> lots of information from the trellis package, which I'm not using. > >> > >> So I decided to try to figure out the native coordinates > of the > >> click in each leaf viewport, to a) see whether the click is within the > > plotting > >> region for that viewport and b) use those coordinates to take the > appropriate > >> action if it is. But I don't seem to be able to figure out how to > translate > > from > >> the top-level viewport coordinates to those of a leaf viewport. I tried > >> interpreting the 3X3 matrix returned by current.transform() as an > affine > >> transformation in the x,y plane in homogeneous coordinates, but could > make no > >> sense of what I was getting. > >> > >> Thanks for any help. -Ben > >> > >> > >> > >> > >> The information transmitted in this electronic > communica...{{dropped:16}} > >> > >> ______________________________________________ > >> 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. > >> > > > > > > > > -- > > http://had.co.nz/ > > > > > > > > The information transmitted in this electronic > communica...{{dropped:16}} > > > > ______________________________________________ > > 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. > > -- > Dr Paul Murrell > Department of Statistics > The University of Auckland > Private Bag 92019 > Auckland > New Zealand > 64 9 3737599 x85392 > [EMAIL PROTECTED] > http://www.stat.auckland.ac.nz/~paul/ > > ______________________________________________ > 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. The information transmitted in this electronic communica...{{dropped:16}} ______________________________________________ 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.
