[R] Writing text in lattice graphics
Deepayan Sarkar
deepayansarkar at yahoo.com
Tue Apr 23 18:33:34 CEST 2002
--- Luis Torgo <ltorgo at liacc.up.pt> wrote:
> I'm trying to obtain a set of regression lines obtained for different values
> of a factor using lattice. I would like to add a string to each panel showing
>
> the R^2 value of the respective line, but I'm having difficulties positioning
>
> the text (namely on which coordinates to give to the "ltext" function).
> Here is what I'm using (I've used ?? for the things I would like you to be so
>
> kind to help me on how to fill in).
>
> > xyplot(O2 ~ Am | Site, data = mydata, scales=list(x='free'),
> panel=function(x,y,...) {
> panel.xyplot(x,y,...)
> panel.lmline(x,y,...)
> ltext(??, ??, round(summary(lm(y ~ x))$r.squared,3))
> })
>
> I would like the R^2 values to appear in the top left corner of each of the
> panels I get.
> I've tried fixed values for the "x", "y" parameters of "ltext", but as I'm
> using different X scales for each panel things get messy...
This is where you can use the flexibility of grid. ltext calls grid.text with
the units fixed at the native x and y scales, but you can get all sorts of
other coordinate systems if you use grid.text directly. For example,
grid.text(round(summary(lm(y ~ x))$r.squared,3), 0.1, 0.9)
should give you approximately what you want. See ?grid.text for details on
how to customize this further.
> I'm using R 1.4.1 on a Windows 2000 machine.
>
> Thank you in advance.
>
> --
> Luis Torgo
> FEP/LIACC, University of Porto Phone : (+351) 22 607 88 30
> Machine Learning Group Fax : (+351) 22 600 36 54
> R. Campo Alegre, 823 email : ltorgo at liacc.up.pt
> 4150 PORTO - PORTUGAL WWW : http://www.liacc.up.pt/~ltorgo
>
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