Bar Graphs - R Graphics - page 62

To make the graph ( Figure 3-30 ), we'll also add a mapping of lg to the color of the points. In-
stead of using grid lines that run all the way across, this time we'll make the lines go only up to
the points, by using geom_segment() . Note that geom_segment() needs values for x , y , xend ,
and yend :

ggplot(tophit, aes(x = avg, y = name)) +
geom_segment(aes(yend = name), xend = 0 , colour = "grey50" ) +
geom_point(size = 3 , aes(colour = lg)) +
scale_colour_brewer(palette = "Set1" , limits = c( "NL" , "AL" )) +
theme_bw() +
theme(panel.grid.major.y = element_blank(),

# No horizontal grid lines

legend.position = c( 1 , 0.55 ), # Put legend inside plot area

legend.justification = c( 1 , 0.5 ))

Another way to separate the two groups is to use facets, as shown in Figure 3-31 . The order in
which the facets are displayed is different from the sorting order in Figure 3-30 ; to change the
display order, you must change the order of factor levels in the lg variable:

ggplot(tophit, aes(x = avg, y = name)) +
geom_segment(aes(yend = name), xend = 0 , colour = "grey50" ) +
geom_point(size = 3 , aes(colour = lg)) +
scale_colour_brewer(palette = "Set1" , limits = c( "NL" , "AL" ), guide = FALSE

FALSE ) +

theme_bw() +
theme(panel.grid.major.y = element_blank()) +
facet_grid(lg ~ . , scales = "free_y" , space = "free_y" )