line graph of four variables in r in just one plot [duplicate] - r

Question

This question already has answers here:
Plotting two variables as lines using ggplot2 on the same graph
(5 answers)
Closed 7 months ago.
I would like to create a line graph that shows how the trend of five air pollutants were during the years 2009 to 2019.
Year
CO2
NO2
O3
PM2.5
2009
30
18
20
30
2010
32
16
22
20
2011
33
16
24
20
2012
32
15
25
22
2013
34
14
27
24
2014
36
14
28
22
2015
38
13
29
20
2016
39
13
30
18
2017
40
12
32
16
2018
44
13
34
15
2019
45
11
38
14
I gave that code but it is a histogram, i would like to have a line graph were all four are in the same plot.
df %>%
ggplot(aes(x = Year, y = n, fill = airpollutants)) +
geom_col() +
facet_wrap(~Year) + ggtitle("trend of airpollutants")
I want this output:
https://cdn.ablebits.com/_img-blog/line-graph/line-graph-excel.png

Answer 1

You could reshape your data from wide to long and colour every airpollutants like this:
df <- read.table(text = "Year CO2 NO2 O3 PM2.5
2009 30 18 20 30
2010 32 16 22 20
2011 33 16 24 20
2012 32 15 25 22
2013 34 14 27 24
2014 36 14 28 22
2015 38 13 29 20
2016 39 13 30 18
2017 40 12 32 16
2018 44 13 34 15
2019 45 11 38 14
", header = TRUE)
library(ggplot2)
library(dplyr)
library(reshape)
df %>%
melt(id = "Year") %>%
mutate(variable = as.factor(variable)) %>%
ggplot(aes(x = Year, y = value, colour = variable)) +
geom_line() +
labs(colour = "airpollutants") +
ggtitle("trend of airpollutants")
Created on 2022-07-26 by the reprex package (v2.0.1)

Answer 2

Usually you'll want to be in long format when plotting in ggplot2.
One way to draw multiple lines without going long is to map over the columns
ggplot(data = df) + purrr::map2(df[-1], names(df[-1]), \(x,y) geom_line(aes(x = df$Year, y = x, col = y))) +
labs(x = "Concentration",
y = "Year",
col = "Pollutant")

Answer 3

set.seed(123)
library(ggplot2)
library(tidyr)
# Example data
df <- data.frame(year = 2009:2019,
CO2 = sample(30:40, 11),
NO2 = sample(10:20, 11),
O3 = sample(20:30, 11),
PM2.5 = sample(15:25, 11))
# Convert to long format
df_long <- pivot_longer(df,
cols = c(CO2, NO2, O3, PM2.5),
values_to = "Concentration",
names_to = "Pollutant")
# Plot
ggplot(df_long,
aes(
x = year,
y = Concentration,
color = Pollutant,
linetype = Pollutant
)) +
geom_line(size = 0.7) +
ggtitle("Trend of Airpollutants") +
xlab("Year") +
ylab("Concentration") +
scale_x_continuous(breaks = seq(2009, 2019, by = 1), limits = c(2009,2019)) +
theme_minimal()