[R] scaling with relative units in plots or retrieving axes limits in plots

[Jannis]

Dears,


a way to define x and y positions in plots in relative numbers (e.g in fractions  between 0 and 1 referring to relative positions inside the plot region) would really help me. One example I would need this to would be to add text via text() to a plot always at a defined spot, e.g the upper left corner. Until now I always determined maximum x and y values and used those, but defining relative positions straight away would be much easier. Possible solutions:

1. Predefined function
Is there anything available that lets me run (for example):

text(0.5,0.5,'middle')

which always puts text on these relative points?



2. Create my own function
It would be straightforward to create my own function that translates the relative number to the axes values in the actual plot, so that 

text(my.function(0.5,0.5),'middle')

would do what I want. For this I would need to be able to somehow retrieve the axis limits for x and y axes. Is there any way I could do this after having called plot()?



Thanks for your help!


Jannis