Plot separate years on a common day-month scale

Question

I want to create a time series plot of temperatures for the summers of 2012 and 2013.

The only problem is that I want the data series to plot one on top of the oth

Answer 1

If your base dataset is temp and date, then this avoids manipulating the original data frame:

ggplot(df) +
  geom_point(aes(x=strftime(date,format="%m-%d"),
                 y=temp, 
                 color=strftime(date,format="%Y")), size=3)+
  scale_color_discrete(name="Year")+
  labs(x="date")

EDIT (Response to OP's comment).

So this combines the approach above with Henrik's, using dates instead of char for the x-axis, and avoiding modification of the original df.

library(ggplot2)
ggplot(df) +
  geom_point(aes(x=as.Date(paste(2014,strftime(date,format="%m-%d"),sep="-")),
                 y=temp, 
                 color=strftime(date,format="%Y")), size=3)+
  scale_color_discrete(name="Year")+
  labs(x="date")