R help - May 2005 - Lattice: how to get default ylim?

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

=========================================================================Research
Scientist, PhD                           Leninsky Prospect 33,
Space Monitoring & Ecoinformation Systems Sector, Moscow, Russia, 119071,
Institute of Ecology,                             Phone: (095) 135-9972;
Russian Academy of Sciences                       Fax: (095) 135-9972

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

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
> 
>
=========================================================================>
Research Scientist, PhD                           Leninsky Prospect 33,
> Space Monitoring & Ecoinformation Systems Sector, Moscow, Russia,
119071,
> Institute of Ecology,                             Phone: (095) 135-9972;
> Russian Academy of Sciences                       Fax: (095) 135-9972
> 
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