R language scatter chart

Scatter charts show many of the points drawn in the Descartes plane. E ach point represents the value of two variables. Select one variable on the horizontal axis and another on the vertical axis.
Use thelot() function to create a simple scatterplot.

Grammar

The basic syntax for creating scatterpics in the R language is -

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

The following is a description of the parameters used -

• x is a dataset whose value is horizontal coordinates.

• y is a dataset whose value is vertical coordinates.

• Main is a block of graphics.

• xlab is a label on the horizontal axis.

• ylab is a label on the vertical axis.

• xlim is the limit of the value of the x used for drawing.

• ylim is the limit of the value of y used for drawing.

• Axes indicate whether two axes should be drawn on the drawing.

Cases

We use the dataset "mtcars" available in the R-language environment to create a basic scatterpic. L et's use the "wt" and "mpg" columns in mtcars.

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

When we execute the code above, it produces the following results -

                    wt      mpg
Mazda RX4           2.620   21.0
Mazda RX4 Wag       2.875   21.0
Datsun 710          2.320   22.8
Hornet 4 Drive      3.215   21.4
Hornet Sportabout   3.440   18.7
Valiant             3.460   18.1

Create a scatter chart

The following script creates a scatterpic of the relationship between wt (weight) and mpg (mile/gallon).

# Get the input values.
input <- mtcars[,c('wt','mpg')]

# Give the chart file a name.
png(file = "scatterplot.png")

# Plot the chart for cars with weight between 2.5 to 5 and mileage between 15 and 30.
plot(x = input$wt,y = input$mpg,
   xlab = "Weight",
   ylab = "Milage",
   xlim = c(2.5,5),
   ylim = c(15,30),		 
   main = "Weight vs Milage"
)
	 
# Save the file.
dev.off()

When we execute the code above, it produces the following results -

Scatter matrix

When we have more than two variables, we want to find a correlation between one variable and the rest, and we use a scatterpic matrix. W e use the pairs() function to create a matrix of scatterpics.

Grammar

The basic syntax for creating a scatterpic matrix in R is -

pairs(formula, data)

The following is a description of the parameters used -

• Formula represents a series of variables used in pairs.

• Data represents the dataset from which the variable will be obtained.

Cases

Each variable is paired with each remaining variable. S catter plots are drawn for each pair.

# Give the chart file a name.
png(file = "scatterplot_matrices.png")

# 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")

# Save the file.
dev.off()

When we execute the code above, we get the following output.