bisig_plot draws the plots of the bivariate signal on the same plot (scale free)
bisig_plot(x, rupt = NULL, mu = NULL, pop = NULL, merge.seg = FALSE)
no value
the signal to be plotted
optional, if given add vertical lines at change points (rupt should a vector)
optional the mean of each class of segment,
optional the cluster to whom each segment belongs to,
should segment be merged ?