How can a line be overlaid on a bar plot using ggplot2?

Question

I\'m looking for a way to plot a bar chart containing two different series, hide the bars for one of the series and instead have a line (smooth if possible) go through the t

Answer 1

You can get group totals in many ways. One of them is

with(df, tapply(val, grp, sum))

For simplicity, you can combine bar and line data into a single dataset.

df_all <- data.frame(grp = factor(levels(df$grp)))
df_all$bar_heights <- with(df, tapply(val, grp, sum))
df_all$line_y <- with(df2, tapply(val, grp, sum))

Bar charts use a categorical x-axis. To overlay a line you will need to convert the axis to be numeric.

ggplot(df_all) +
   geom_bar(aes(x = grp, weight = bar_heights)) +
   geom_line(aes(x = as.numeric(grp), y = line_y))