Q:

Grouped bar chart with date on x-axis

I'm getting back to R, and I have some trouble plotting the data I want.
It's in this format :
date         value1    value2
10/25/2016   50        60
12/16/2016   70        80
01/05/2017   35        45

And I would like to plot value1 and value2 next to each other, with the corresponding date on the x axis. So far I have this, I tried to plot only value1 first :
df$date <- as.Date(df$date, "%m/%d/%Y")
ggplot(data=df,aes(x=date,y=value1))

But the resulting plot doesn't show anything. The maximum values on the x and y axis seem to correspond to the ranges of my dataframe, but why is nothing showing up?
It works with plot(df$date,df$value1) though, so I don't get what I am doing wrong.

A:

the ggplot call alone does not actually create any layers on the plot. You need to add a geom. 
For this you probably want geom_point() or geom_line()
ggplot(data=df,aes(x=date,y=value1)) +
  geom_point()

or
ggplot(data=df,aes(x=date,y=value1)) +
  geom_line()

or you could do both if you want points and lines
ggplot(data=df,aes(x=date,y=value1)) +
  geom_point() +
  geom_line()

If you want both values on the plot, I would recommend doing some data manipulation first with the tidyr package.
df %>%
  gather(key = "group", value = "value", value1:value2) %>%
  ggplot(aes(date, value, color = group, group = group)) +
    geom_line()

