[R] ggplot: Axis lines

[Pedro de Barros]

Dear All,

I am trying to print some simple ggplot plots, but I would like to 
have no gridlines, and no border.
I have achieved this using ggopt(grid.lines='NA', border.lines='NA').

However, this also clears the axis lines, and reading the help, it 
looks like the "axis" objects have only two slots, "label" and "ticks".

How can I get rid of gridlines and border, and still keep the axis lines?

Thanks,
Pedro