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