Time-series plot for different seasons in the same plot

Question

I would like plot a time series data for different seasons of the year (grouped as cold or warm) in the same plot and identify the two periods. How can I do that?

Reproducible data follows:

library(gamair) 
data(chicago) 
chicago$date<-seq(from=as.Date("1987-01-01"), to=as.Date("2000-12-31"),length=5114)
data.cold <- subset(chicago, quarters(date) %in% c("Q1", "Q4"))
data.warm <- subset(chicago, quarters(date) %in% c("Q2", "Q3"))

These codes below will create two separate plots for the two periods:

with(data.cold,plot(date,death,pch=".", ylab= expression("Mortality Count"), main = "Daily Mortality in cold season"))
with(data.warm ,plot(date,death,pch=".", ylab= expression("Mortality Count"), main = "Daily Mortality in warm season"))

This following code creates one plot, but there is no clear demarcation of the two periods. My wish is to create identifiable plot for the two periods in a single plot.

with(chicago,plot(date,death,pch=".", ylab= expression("Mortality Count"), main = "Daily Mortality from  1987-2000"))

Answer 1

Have a look at ?points :

with(data.cold,plot(date,death,pch=".", ylab= expression("Mortality Count"), main = "Daily Mortality in cold season"))
with(data.warm ,points(date,death,pch=".", ylab= expression("Mortality Count"), main = "Daily Mortality in warm season", col="red"))
legend("topright", c("cold", "warm"), fill=c("black", "red"))

Does that work for you?