default_background_ticks_gridlines.R

plot + 
  theme(panel.background = element_blank(),
        axis.ticks = element_blank(),
        # hide the minor grid lines
        panel.grid.minor = element_blank(),
        # hide vertical major grid lines
        panel.grid.major.x = element_blank(),
        # change colour and thickness of horizontal grid lines
        panel.grid.major.y = element_line(colour = "#757575", size = 0.3))