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Scatter plots in R Language

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  • Last Updated : 10 Dec, 2021

A scatter plot is a set of dotted points to represent individual pieces of data in the horizontal and vertical axis. A graph in which the values of two variables are plotted along X-axis and Y-axis, the pattern of the resulting points reveals a correlation between them.

R – Scatter plots

We can create a scatter plot in R Programming Language using the plot() function.

Syntax: plot(x, y, main, xlab, ylab, xlim, ylim, axes)

Parameters: 

  • x: This parameter sets the horizontal coordinates.
  • y: This parameter sets the vertical coordinates.
  • xlab: This parameter is the label for horizontal axis.
  • ylab: This parameter is the label for vertical axis.
  • main: This parameter main is the title of the chart.
  • xlim: This parameter is used for plotting values of x.
  • ylim: This parameter is used for plotting values of y.
  • axes: This parameter indicates whether both axes should be drawn on the plot.

Simple Scatterplot Chart

In order to create Scatterplot Chart:

  1. We use the data set “mtcars”.
  2. Use the columns “wt” and “mpg” in mtcars.

Example: 

R




input <- mtcars[, c('wt', 'mpg')]
print(head(input))

Output:

Creating a Scatterplot Graph

In order to create a Scatterplot graph: 

  1. We are using the required parameters to plot the graph.
  2. In this ‘xlab’ describes the X-axis and ‘ylab’ describes the Y-axis.

Example: 

R




# Get the input values.
input <- mtcars[, c('wt', 'mpg')]
 
# Plot the chart for cars with
# weight between 1.5 to 4 and
# mileage between 10 and 25.
plot(x = input$wt, y = input$mpg,
    xlab = "Weight",
    ylab = "Milage",
    xlim = c(1.5, 4),
    ylim = c(10, 25),       
    main = "Weight vs Milage"
)

Output: 

Scatterplot Matrices

When we have two or more variables and we want to correlate between one variable and others so we use a scatterplot matrix.

pairs() function is used to create matrices of scatterplots.

Syntax: pairs(formula, data)

Parameters: 

  • formula: This parameter represents the series of variables used in pairs.
  • data: This parameter represents the data set from which the variables will be taken.

Example: 

R




# Plot the matrices between
# 4 variables giving 12 plots.
 
# One variable with 3 others
# and total 4 variables.
pairs(~wt + mpg + disp + cyl, data = mtcars,
    main = "Scatterplot Matrix")

Output: 

Scatterplot with fitted values

In order to create Scatterplot Chart: 

  1. We are using the ggplot2 package provides ggplot() and geom_point() function for creating a scatterplot.
  2. Also we are using the columns “wt” and “mpg” in mtcars.

Example: 

R




# Loading ggplot2 package
library(ggplot2)
     
# Creating scatterplot with fitted values.
# An additional function stst_smooth
# is used for linear regression.
ggplot(mtcars, aes(x = log(mpg), y = log(drat))) +
        geom_point(aes(color = factor(gear))) +
        stat_smooth(method = "lm",
        col = "#C42126", se = FALSE, size = 1
)

Output:

Adding title with dynamic name

To create Scatterplot Chart, Add a sub-title: 

  1. We use the additional function, In ggplot we add the data set “mtcars” with this adding ‘aes’, ‘geom_point’.
  2. Use the Title, Caption, Subtitle.

Example: 

Python3




# Loading ggplot2 package
library(ggplot2)
     
# Creating scatterplot with fitted values.
# An additional function stst_smooth
# is used for linear regression.
new_graph<-ggplot(mtcars, aes(x = log(mpg),
                              y = log(drat))) +
                    geom_point(aes(color = factor(gear))) +
                    stat_smooth(method = "lm",
                                col = "#C42126",
                    se = FALSE, size = 1)
 
# in above example lm is used for linear regression
# and se stands for standard error.
# Adding title with dynamic name
new_graph + labs(
        title = "Relation between Mile per hours and drat",
        subtitle = "Relationship break down by gear class",
        caption = "Authors own computation"
)

Output:

3D Scatterplots

Here we will use scatterplot3D package to create 3D scatterplots, this package can plot scatterplot in 3D using scatterplot3d() methods.

R




# 3D Scatterplot
library(scatterplot3d)
attach(mtcars)
 
scatterplot3d(mpg, cyl, hp,
              main = "3D Scatterplot")

Output:


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