Scatter plots in R Language

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

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: Sets the horizontal coordinates.
• y: Sets the vertical coordinates.
• xlab: Label for the horizontal axis.
• ylab: Label for the vertical axis.
• main: Title of the chart.
• xlim: Defines the x-axis range.
• ylim: Defines the y-axis range.
• axes: Indicates whether both axes should be drawn.

Loading the Data

In order to create Scatterplot Chart, we use the data set "mtcars". We will use the columns "wt" and "mpg" in mtcars.

Example: 

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

Output:

1. Creating a Scatterplot Graph

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

Example: 

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

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: 

2. Scatterplot Matrices

When we have two or more variables and we want to correlate between one variable and others so we use a R scatterplot matrix. The pairs() function is used to createR  matrices of scatterplots.

Syntax:

pairs(formula, data)

Parameters: 

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

Example: 

pairs(~wt + mpg + disp + cyl, data = mtcars,
       main = "Scatterplot Matrix")

Output: 

3. Scatterplot with fitted values

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

Example: 

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

3.1 Adding title with dynamic name

In ggplot we add the data set "mtcars" with this adding 'aes', 'geom_point'. We will use the Title, Caption, Subtitle.

Example: 

library(ggplot2)
    
new_graph<-ggplot(mtcars, aes(x = log(mpg),
                              y = log(drat))) +
                    geom_point(aes(color = factor(gear))) +
                    geom_smooth(method = "lm",
                                col = "#C42126",
                    se = FALSE, size = 1)

new_graph + labs(
        title = "Relation between Mile per hours and drat",
        subtitle = "Relationship break down by gear class",
        caption = "Authors own computation")

Output:

4. 3D Scatterplots

Here we will use the plotly package to create interactive 3D scatter plots. The plot_ly() method in plotly can be used to create 3D scatter plots, where you can define the x, y, and z coordinates for the points.

install.packages("plotly")
library(plotly)

data(mtcars)

fig <- plot_ly(data = mtcars, 
               x = ~mpg, 
               y = ~wt, 
               z = ~qsec, 
               type = 'scatter3d', 
               mode = 'markers', 
               marker = list(color = 'blue', size = 5))

fig <- fig %>% layout(title = '3D Scatter Plot of mtcars',
                      scene = list(
                        xaxis = list(title = 'Miles Per Gallon (mpg)'),
                        yaxis = list(title = 'Weight (wt)'),
                        zaxis = list(title = '1/4 Mile Time (qsec)')
                      ))

fig

Output: