ggplot2 time series plotting: how to omit periods when there is no data points?

Question

I have a time series with multiple days of data. In between each day there's one period with no data points. How can I omit these periods when plotting the time series using ggplot2?

An artificial example shown as below, how can I get rid of the two periods where there's no data?

code:

Time = Sys.time()+(seq(1,100)*60+c(rep(1,100)*3600*24, rep(2, 100)*3600*24, rep(3, 100)*3600*24))
Value = rnorm(length(Time))
g <- ggplot() 
g <- g + geom_line (aes(x=Time, y=Value))
g

Answer 1

First, create a grouping variable. Here, two groups are different if the time difference is larger than 1 minute:

Group <- c(0, cumsum(diff(Time) > 1))

Now three distinct panels could be created using facet_grid and the argument scales = "free_x":

library(ggplot2)
g <- ggplot(data.frame(Time, Value, Group)) + 
  geom_line (aes(x=Time, y=Value)) +
  facet_grid(~ Group, scales = "free_x")

Answer 2

The problem is that how does ggplot2 know you have missing values? I see two options:

1. Pad out your time series with NA values

2. Add an additional variable representing a "group". For example,

   dd = data.frame(Time, Value)
   ##type contains three distinct values
   dd$type = factor(cumsum(c(0, as.numeric(diff(dd$Time) - 1))))
   
   ##Plot, but use the group aesthetic
   ggplot(dd, aes(x=Time, y=Value)) +
         geom_line (aes(group=type))
   

   gives