p1 <- ggplot(data = DNA_result, mapping = aes( x= num, y = nd)) +
geom_point(colour = "red") +
xlab( "樣本序號") +
ylab("濃度")+
theme(plot.caption = element_text(hjust = 0))+ theme_bw()
p1
p2 <- ggplot(data = DNA_result, mapping = aes( x= num, y = A280)) +
geom_point(colour = "blue") +
xlab( "樣本序號") +
ylab("A260/A280")+
theme(plot.caption = element_text(hjust = 0))+ theme_bw() %+replace%
theme(panel.background = element_rect(fill = NA))
p2
double_y_axis <- function(p1, p2){
g1 <- ggplot_gtable(ggplot_build(p1))
g2 <- ggplot_gtable(ggplot_build(p2))
# overlap the panel of 2nd plot on that of 1st plot
pp <- c(subset(g1$layout, name == "panel", se = t:r))
g <- gtable_add_grob(g1, g2$grobs[[which(g2$layout$name == "panel")]], pp$t, pp$l, pp$b, pp$l)
# axis tweaks
ia <- which(g2$layout$name == "axis-l")
ga <- g2$grobs[[ia]]
ax <- ga$children[[2]]
ax$widths <- rev(ax$widths)
ax$grobs <- rev(ax$grobs)
ax$grobs[[1]]$x <- ax$grobs[[1]]$x - unit(1, "npc") + unit(0.15, "cm")
g <- gtable_add_cols(g, g2$widths[g2$layout[ia, ]$l], length(g$widths) - 1)
g <- gtable_add_grob(g, ax, pp$t, length(g$widths) - 1, pp$b)
# draw it
grid.draw(g)
return(g)
}
double_y_axis(p1,p2)
ref3