add_sig_line_to_plot: Add a Cox regression statistical significance line
Description
This function will add a Cox regression statistical significance line to the
input ggplot2.
Usage
add_sig_line_to_plot(cur_plot, coord_flip, add_sig_line)
Arguments
cur_plot
ggplot2 object to add on to.
coord_flip
Boolean to indicate if the ggplot2 has been flipped or not.
add_sig_line
Boolean to indicate whether the significance line should
be added or not.