plot multiple lines in ggplot

Question

I need to plot hourly data for different days using ggplot, and here is my dataset:

The data consists of hourly observations, and I want to plot each day's observation into one separate line.

Here is my code

xbj1 = bj[c(1:24),c(1,6)]

xbj2 = bj[c(24:47),c(1,6)] xbj3 = bj[c(48:71),c(1,6)]

ggplot()+
geom_line(data = xbj1,aes(x = Date, y= Value), colour="blue") +
geom_line(data = xbj2,aes(x = Date, y= Value), colour = "grey") + 
geom_line(data = xbj3,aes(x = Date, y= Value), colour = "green") +
xlab('Hour') +
ylab('PM2.5')

Please advice on this.

Answer 1

I'll make some fake data (I won't try to transcribe yours) first:

set.seed(2)
x <- data.frame(
  Date = rep(Sys.Date() + 0:1, each = 24),
  # Year, Month, Day ... are not used here
  Hour = rep(0:23, times = 2),
  Value = sample(1e2, size = 48, replace = TRUE)
)

This is a straight-forward ggplot2 plot:

library(ggplot2)
ggplot(x) +
  geom_line(aes(Hour, Value, color = as.factor(Date))) +
  scale_color_discrete(name = "Date")

ggplot(x) +
  geom_line(aes(Hour, Value)) +
  facet_grid(Date ~ .)

I highly recommend you find good tutorials for ggplot2 , such as http://www.cookbook-r.com/Graphs/ . Others exist, many quite good.