Add colored line segments to a plot

This function adds colored line segments to an existing plot. The line is plotted at points specified by inputs x and y, and colored according to factor input z (with one color for each level of z).

cline(x, y, z, color_vector)

Arguments

x	x positions of points to be plotted
y	y positions of points to be plotted
z	a factor, the same length as x and y. Line segments in the resulting plot will be colored according to the levels of z.
color_vector	a list of colors to use (length should match the number of levels in z).

Examples

cline(x=ChickWeight$Time, y=ChickWeight$weight, 
      z=as.factor(ChickWeight$Diet), 
      color_vector=c('black', 'grey20', 
                     'grey50', 'grey70'))