Create an object defining the breaks on an axis.
amAxisBreaks(
values = NULL,
labels = NULL,
interval = NULL,
timeInterval = NULL
)positions of the breaks, a vector of values; for a date axis, this must be a vector of dates
if values is given, the labels of the breaks; if
NULL, the labels are set to the values
for equally spaced breaks, the number of pixels between two
consecutive breaks; ignored if values is given
for equally spaced breaks on a date axis, this option
defines the interval between two consecutive breaks; it must be a string
like "1 day", "7 days", "1 week", "2 months",
...; ignored if values or interval is given