point size, default to 1 of nobs<1000, 0.4 if nobs>1000
alpha0
alpha of point
dilute
a number or logical, dafault to TRUE, will plot
nrow(data_long)/dilute data. For example, if dilute = 5 will plot
1/5 of the data. if dilute = TRUE will plot half of the data.
add_abline
default to FALSE, add a diagonal line ggExtra::ggMarginal
but notice if add histogram, what is returned is no longer a ggplot2 object
add_hist
optional to add marginal histogram using
ggExtra::ggMarginal but notice if add histogram, what is returned is no
longer a ggplot2 object