Adding a second y-axis and line over a bar plot - r

Question

Following is my data
df <- data.frame(Lab = c("Queen II", "MMH", "Berea", "Maluti", "Motebang"),
Expected = c(13200, 5280, 5280, 2640, 5280),
Actual = c(8759, 761, 2263, 2210, 6100),
utili_pct = c(66.35, 14.41, 42.86, 83.71, 115.53))
and I have tried to plot a bar chat which includes a line over the chart.
step 1
# I Converted numeric variable "Actual" to a factor
df$Actualx <- as.factor(df$Actual)
This was so that I could plot a chart with two-factor variables vs one numeric
So I tidy the data and ran the plot this way but the axis scale became no ordered.
tidy_Data = df %>% gather(key, value, Actualx, Expected)
ggplot(tidy_Data, aes(x=Lab, y=value, fill=key)) +
geom_bar(stat = "identity", position = position_dodge(0.8)) `
Futhermore,
I tried to add a line utili_ptc and the second axis, but the scale is giving me a hard time,
The line does not align with the bars.
ggplot(tidy_Data, aes(x=Lab, y=value, fill=key)) +
geom_bar(stat = "identity", position = position_dodge(0.8)) +
geom_line(aes(x=Lab, y=utili_pct), color = "green", group = 1)

Answer 1

There's a post about why using a seconday y-axis is frowned upon here
ggplot with 2 y axes on each side and different scales
To answer your specific question, I did a quick search and found this post and used it construct your diagram. Please have a look at it and see if you can understand
https://rpubs.com/kohske/dual_axis_in_ggplot2
library(ggplot2)
library(gtable)
library(grid)
grid.newpage()
# two plots
p1 <- ggplot(tidy_Data, aes(x=Lab, y=value, fill=key)) +
geom_bar(stat = "identity", position = position_dodge(0.8)) +
theme(legend.position = 'top')
p2 <- ggplot(tidy_Data, aes(x = 1:10, y = utili_pct)) + geom_line() +
theme_bw() +
theme(panel.background = element_rect(fill = NA))
g1 <- ggplot_gtable(ggplot_build(p1))
g2 <- ggplot_gtable(ggplot_build(p2))
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)

Answer 2

Thank you very very much for your guidance. I have finally been able to plot the chart the way I wanted using your code.
library("tidyverse")
library("ggplot2")
library("gtable")
library("grid")
df <- data.frame(Lab = c("Queen II", "MMH", "Berea", "Maluti", "Motebang"), Actual = c(8759, 761, 2263, 2210, 5100), utili_pct = c(66.35, 14.41, 42.86, 83.71, 96.59), Expected = c(13200, 5280, 5280, 2640, 5280),stringsAsFactors = F)
tidy the data
tidy_Data <- df%>% gather(key,value, Actual, Expected)
grid.newpage()
two plots
p1 <- ggplot(tidy_Data, aes(x=Lab, y=value, fill=key)) + geom_bar(stat = "identity", position = position_dodge(0.8)) + theme(legend.position = "bottom")
p2 <- ggplot(df, aes(x=1:5, y=utili_pct)) + geom_line() + ylim(10,100) + theme_bw() + theme(panel.background = element_rect(fill = NA))
extract gtable
g1 <- ggplot_gtable(ggplot_build(p1))
g2 <- ggplot_gtable(ggplot_build(p2))
Overlap the panel of the 2nd plot on that of the 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)