Lattice: how to get default ylim?

On Thursday 19 May 2005 8:00 am, David James wrote:

Hi,

Within your panel function you can use current.viewport() to recover
the active grid viewport and get xlim/ylim (in addition to other very
useful information).  Then you can use grid.text (plus any other
grid.* function), e.g.,

  require(grid)

  my.panel <-
  function(...)
  {
     panel.xyplot(...)

     ## add "Hello World on the top-left of each panel

     v <- current.viewport()        ## requires R 2.1.0 (I believe)

No, I think it's been there for a while. However, AFAIR the fact that 
viewports have components xscale and yscale that can be accessed like this is 
undocumented and may change if the implementation changes (which is a real 
possibility). 

Ideally, there should be exported interfaces to access this information, 
either in grid or lattice. One of the reasons there isn't is that you rarely 

need it, including in this example (see below).

     xlim <- v$xscale
     ylim <- v$yscale
     grid.text(x = xlim[1], y = ylim[2], default.units="native",
        label = "Hello World", just= c("left", "top"))

An equivalent version where you don't need xlim and ylim is 

     grid.text(x = 0, y = 1, default.units="npc",
        label = "Hello World", just= c("left", "top"))

Deepayan

  }

Hope this helps.

--
David

Wladimir Eremeev wrote:

Dear r-help,

  I draw graphics with xyplot and want to add some text to each panel
  (actually, the slope, error and significance of a regression line).

  I have defined the function, drawing a single panel and pass it to
  xyplot in the panel argument. This function calls panel.xyplot,
  calculates linear regression and formats coefficients.

  Now I want the text, I mentioned above, to be put in the upper left
  corner of each plot.
  I use ltext, and I need to define coordinates x and y.
  In order to do this I need to know the limits of x and y axes.

  I do not want to pass arguments xlim and ylim to the xyplot function
  and want it to calculate them automatically.
  And I also want to know the result of calculations. :)
  How to do this?

  Thank you very much.

--
Best regards
Wladimir Eremeev                                     mailto:wl at eimb.ru

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