where to place the labels in user units, as in axis
labels
text strings
nlines
How many lines to use to stagger the labels.
top.line
Distance from the axis to place the first line of text.
line.spacing
Spacing between lines of text labels.
Value
nil
Details
This function is mainly useful when either long axis labels or a large
number of labels are to be placed without overlapping. It places the
labels regularly spaced and staggered along the axis specified.