character string specifying the plot components. Allowed values
include:
"grid" for both x and y grids
"x.grid" for x axis grids
"y.grid" for y axis grids
"axis" for both x and y axes
"x.axis" for x axis
"y.axis" for y axis
"xlab", or "x.title"
for x axis label
"ylab", or "y.title" for y axis label
"xylab", "xy.title" or "axis.title" for both x and y axis
labels
"x.text" for x axis texts (x axis tick labels)
"y.text" for y axis texts (y axis tick labels)
"xy.text" or "axis.text" for both x and y axis texts
"ticks" for both x and y ticks
"x.ticks" for x ticks
"y.ticks" for y ticks
"legend.title" for the legend title
"legend" for the legend