a value between 0 to 1, specifying the effective size of the circle plot area in the current window. The smaller the size, the larger the blank area around the circle plot.
oma
A vector of the form c(bottom, left, top, right) giving the size of the outer margins in lines of text.
mar
A numerical vector of the form c(bottom, left, top, right) which gives the number of lines of margin to be specified on the four sides of the plot.
Author
Minghui Wang <m.h.wang@live.com>
Details
After setting up, the extremes of the user coordinates of the plotting region can be found out by par('usr').