- nr
 
number of circles. When NULL, as per default, the grid aligns with the tick marks on the corresponding default axis
   (i.e., tickmarks as computed by axTicks). When NA, no circular grid lines are drawn.
  
- ntheta
 
number of radial grid lines. Defaults to 12 uniformly distributed between 0 and 2*pi (each pi/3).
  
- col
 
character or (integer) numeric; color of the grid lines.
  
- lty
 
character or (integer) numeric; line type of the grid lines.
  
- lwd
 
non-negative numeric giving line width of the grid lines.
   
- rlabels
 
the radius labels. Use NA if no labels should be to be added.
  
- alabels
 
the labels for the angles, they are printed on a circle outside the plot. Use NA for no angle labels.
  
- lblradians
 
logic, defines if angle labels will be in degrees (default) or in radians.
- cex.lab
 
the character extension for the labels.
- las
 
alignment of the labels, 1 means horizontal, 2 radial and 3 vertical.
 
- adj
 
adjustments for the labels. (Left: 0, Right: 1, Mid: 0.5) The default is 1 for the levels on the right side of the circle, 0 for labels on the left and 0.5 for labels exactly on north on south.
- dist
 
gives the radius for the labels, in user coordinates. Default is par("usr")[2] * 1.07.