overlapping line and bar charts at the dame time with ggplot - r

Question

Would like to overlap a line chart over a bar chart with ggplot.
Say, V1, V2 are the data for the bar charts, and V3 shall be presented as line.
How can I complete the subset and different geom at the same time?
library(data.table)
library(ggplot2)
set.seed(100)
dat <- data.frame(Axis=letters[1:10],V1=1:10, V2=runif(10, 1,10), V3=10:1)
dat <-melt(data,id.var="Axis",measure.var=c("V1","V2","V3"))
Would it be like this?
ggplot(dat, aes(x=Axis)) +
geom_bar(stat="identity", aes(, y= value[------]))+ # V1, V2 for bars
geom_line(aes(y=value[-----)) # V3 for line
I tried making the subset of V1, V2, and make a bar chart, but can't insent V3 as a line on the chart.
Many thanks
Thanks to #dash2, I slightly changed his code, and make it looks clearer.
ggplot(dat, aes(x = Axis)) +
geom_col(aes(y = V1), fill = "darkred", alpha = .5, width=0.4) +
geom_col(aes(y = V2), fill = "blue", alpha = .5,
position = position_nudge(x = 0.4),width=0.4) +
geom_line(aes(y = V3, group = NA))

Answer 1

Simplest, no melting.
ggplot(data, aes(x = Axis)) +
geom_col(aes(y = V1), fill = "darkred", alpha = .5) +
geom_col(aes(y = V2), fill = "blue", alpha = .5,
position = position_nudge(x = 0.2)) +
geom_line(aes(y = V3, group = NA))
Add aesthetics to taste.
The group argument is necessary. I think that discrete scales (like the x axis here) automatically group their values, leaving you with groups of 1 and no lines being drawn... consistent, but unintuitive.

Answer 2

No need to melt your data, just simply add different aesthetics to each geom:
data <- data.frame(Axis=letters[1:10], V1=1:10, V2=runif(10, 1,10), V3=10:1)
ggplot(data, aes(x = V1)) +
geom_col(aes(y = V2)) +
geom_line(aes(y = V3))

Answer 3

How about this
library(data.table)
library(ggplot2)
set.seed(100)
data <- tibble(Axis=letters[1:10],V1=1:10, V2=runif(10, 1,10), V3=10:1)
data <-melt(data,id.var="Axis",measure.var=c("V1","V2","V3"))
glimpse(data)
ggplot(data, aes(x=Axis, y= data$value)) +
geom_bar(aes(fill = variable), stat="identity")

Answer 4

Another option could be with melt data as:
library(data.table)
library(ggplot2)
set.seed(100)
data <- data.frame(Axis=letters[1:10],V1=1:10, V2=runif(10, 1,10), V3=10:1)
data <-melt(data,id.var="Axis",measure.var=c("V1","V2","V3"))
library(dplyr)
ggplot() +
geom_bar(data=filter(data, variable %in% c("V1", "V2")),
aes(x = Axis, y = value, fill=variable), stat ="identity", position="dodge") +
geom_line(data=filter(data, variable == "V3"),
aes(x = Axis, y = value, colour = variable, group=variable))