if y is not NULL, this argument is a numeric
vector containing the abscissa (x-axis) values for
the current plot. If y=NULL, this argument is taken as a numeric
vector of ordinate (y-axis) values.
cex
par function character expansion value. Default: 1.
col
par function color value for the text. Default: 1.
nquadrant
an integer denoting the number of quadrants to partition
the space spanned by x and y. For example, if nquadrants=3, the
x-y space is partitioned into a 3x3 grid of equisized blocks. Default: 5.
text.
a character string to place in the current plot.
Default: ""
y
a numeric vector containing the ordinate (y-axis) values
in the current plot. If NULL, the x input argument is taken
as the y-axis values while the x-axis values are extracted from
x via the positions function. If there are
no positions available, then the sequence 1:length(x) is used
as the x-axis positions. Default: NULL.