Plot Lines from a List of DataFrames using ggplot2 in R

For data visualization, the ggplot2 package is frequently used because it allows us to create a wide range of plots. To effectively display trends or patterns, we can combine multiple data frames to create a combined plot.

Syntax:

ggplot(data = NULL, mapping = aes(), colour())

Parameters:

• data – Default dataset to use for plot.
• mapping – List of aesthetic mappings to use for plot.

Installation of Required Packages

To get started, you need to install and load the necessary libraries:

install.packages("ggplot2")
install.packages("dplyr")
library(ggplot2)
library(dplyr)

Example 1: Plotting Multiple DataFrames

Here, we will create a list of data frames and plot them combined using ggplot2. Each data frame will be a set of values, and the lines from each data frame will be separated by colors

df1 = data.frame(col1=c(1: 10), col2=rnorm(10))
df2 = data.frame(col1=c(5: 10), col2=rnorm(6))
df3 = data.frame(col1=c(2: 12), col2=rnorm(11))

samplelist = list(df1, df2, df3)

# plotting the data
graph <- ggplot(bind_rows(samplelist, .id="data_frame"), 
                 aes(col1, col2, colour=data_frame)) +
geom_line()

print(graph)

Output

[1] "First Dataframe"
    col1      col2
1     1   2.6799001
2     2   1.6732359
3     3  -0.2821830
4     4   0.6951255
5     5   0.3629730
6     6   1.6543411
7     7   0.9301622
8     8   0.6858366
9     9   1.3150289
10   10  -0.9306804
[1] "Second Dataframe"
   col1      col2
1    5  -0.1813050
2    6   1.3543525
3    7   0.0810269
4    8   0.1788353
5    9   1.5264921
6   10   0.3677910
[1] "Third Dataframe"
    col1    col2
1     2  -1.0602057
2     3  -0.6040208
3     4   1.9346507
4     5   0.5183120
5     6   0.7176499
6     7   0.2908290
7     8   1.4760342
8     9   0.5935123
9    10   0.3882407
10   11   0.8871490
11   12  -0.3974801

Plot lines from a list of data frames using ggplot2 in R

Explanation:

• bind_rows() binds the data frames together, and .id creates a new column, data_frame, to specify the source of each row.
• aes() maps col1 to the x-axis, col2 to the y-axis, and data_frame to the color aesthetic.
• geom_line() is used to place lines on the plot according to the data points. 

Example 2: Handling Non-Numeric Data

Here, we deal with non-numeric data like characters or letters in the columns and apply geom_line() to plot the data.

d1 = data.frame(col1=c(1: 10), col2=letters[1:5])
d2 = data.frame(col1=c(7: 9), col2=letters[5:7])
d3 = data.frame(col1=c(1: 6), col2=rep('e', 6))
d4 = data.frame(col1=c(5, 9, 10), col2=c('x', 'm', 'n'))

print("First DataFrame")
print(d1)
print("Second DataFrame")
print(d2)
print("Third DataFrame")
print(d3)
print("Fourth DataFrame")
print(d4)

samplelist = list(df1, df2, df3, df4)

# plotting the data
graph <- ggplot(bind_rows(samplelist, .id="data_frame"), 
                 aes(col1, col2, colour=data_frame)) +
geom_line()

print(graph)

Output

[1] "First DataFrame"
> print(df1)
  col1 col2
1     1    a
2     2    b
3     3    c
4     4    d
5     5    e
6     6    a
7     7    b
8     8    c
9     9    d
10   10    e
> print ("Second DataFrame")
[1] "Second DataFrame"
> print(df2)
 col1 col2
1    7    e
2    8    f
3    9    g
> print ("Third DataFrame")
[1] "Third DataFrame"
> print(df3)
 col1 col2
1    1    e
2    2    e
3    3    e
4    4    e
5    5    e
6    6    e
> print ("Fourth DataFrame")
[1] "Fourth DataFrame"
> print(df4)
 col1 col2
1    5    x
2    9    m
3   10    n

Plot lines from a list of data frames using ggplot2 in R

Explanation:

• The columns contain alphabetic characters instead of numeric values,but the method to combine and plot them is exactly the same.
• The plot created will display lines joining the points according to character data, where each line has a different color.

Related Articles:

• R Programming Language – Introduction
• dplyr Package in R Programming