How do i join points within a ggplot in R properly? - r

Question

I used the code below to create my plot above. Is there a way to adapt my code so that I do not have the long red line joining the two periods of non-peak hours?
Day_2 <- non_cumul[(non_cumul$Day.No == 'Day 2'),]
Day_2$time_test <- between(as.ITime(Day_2$date_time),
as.ITime("09:00:00"),
as.ITime("17:00:00"))
Day2plot <- ggplot(Day_2,
aes(date_time, non_cumul_measurement, color = time_test)) +
geom_point()+
geom_line() +
theme(plot.title = element_text(hjust = 0.5)) +
ggtitle('Water Meter Averages (Thurs 4th Of Jan 2018)',
'Generally greater water usage between peak hours compared to non peak hours') +
xlab('Date_Times') +
ylab('Measurement in Cubic Feet') +
scale_color_discrete(name="Peak Hours?")
Day2plot +
theme(axis.title.x = element_text(face="bold", colour="black", size=10),
axis.text.x = element_text(angle=90, vjust=0.5, size=10))

Answer 1

From the sound of it, your plot comprises of one observation for each position on the x-axis, and you want consecutive observations of the same color to be joined together in a line.
Here's a simple example that reproduces this:
set.seed(5)
df = data.frame(
x = seq(1, 20),
y = rnorm(20),
color = c(rep("A", 5), rep("B", 9), rep("A", 6))
)
ggplot(df,
aes(x = x, y = y, color = color)) +
geom_line() +
geom_point()
The following code creates a new column "group", which takes on a different value for each collection of consecutive points with the same color. "prev.color" and "change.color" are intermediary columns, included here for clarity:
library(dplyr)
df2 <- df %>%
arrange(x) %>%
mutate(prev.color = lag(color)) %>%
mutate(change.color = is.na(prev.color) | color != prev.color) %>%
mutate(group = cumsum(change.color))
> head(df2, 10)
x y color prev.color change.color group
1 1 -0.84085548 A <NA> TRUE 1
2 2 1.38435934 A A FALSE 1
3 3 -1.25549186 A A FALSE 1
4 4 0.07014277 A A FALSE 1
5 5 1.71144087 A A FALSE 1
6 6 -0.60290798 B A TRUE 2
7 7 -0.47216639 B B FALSE 2
8 8 -0.63537131 B B FALSE 2
9 9 -0.28577363 B B FALSE 2
10 10 0.13810822 B B FALSE 2
ggplot(df2,
aes(x = x, y = y, color = colour, group = group)) +
geom_line() +
geom_point()