ggplot(fortify(n, arrow.gap = 0), aes(x, y, xend = xend, yend = yend)) + geom_edges(color = "white", alpha = 0.5) + geom_nodes(aes(color = period, size = log10(degree))) + guides(alpha = FALSE, size = FALSE) + scale_color_manual(values = wes_palette("Zissou")[ c(1, 3, 4, 5)]) + theme_blank(14) + theme(rect = element_rect(fill = "grey10"), panel.background = element_rect(fill = "grey10"), text = element_text(color = "white"), legend.position = "bottom")