Grid and Lattice Packages in R Programming

Grid and Lattice Packages in detail

Every programming language offers packages to implement various functions. In R programming, packages bundle related functions to streamline development. To utilize these functions, installing and loading the respective packages is necessary. The CRAN repository hosts over 10,000 R packages. Notable packages like Grid and Lattice in R are used to implement graphical functions to create visual outputs such as rectangles, circles, histograms, bar plots, etc.

Grid Package in R

The Grid package, previously part of the CRAN repository, is now included as a base package in R. It serves as the foundation for advanced graphical functions in other packages like lattice and ggplot2. Moreover, it can modify lattice-generated outputs. Being a base package, it doesn’t require separate installation as it comes pre-installed with R.

To load the Grid package, use the following command in the console and select “grid” when prompted:

local({pkg <- select.list(sort(.packages(all.available = TRUE)), graphics = TRUE)
if(nchar(pkg)) library(pkg, character.only = TRUE)})

The Grid package provides several functions to create graphical objects, also known as “grobs.” Some of the functions include:

• circleGrob
• linesGrob
• polygonGrob
• rasterGrob
• rectGrob
• segmentsGrob
• legendGrob
• xaxisGrob
• yaxisGrob

To see the complete list of functions in the Grid package, use the following command:

library(help = "grid")

Example: Using the Grid Package

The following example demonstrates how to create and save graphical objects using the Grid package:

library(grid)

# Save output as a PNG file
png(file = "grid_example.png")

# Create a circular grob
circle <- circleGrob(name = "circle", x = 0.4, y = 0.4, r = 0.3,
                     gp = gpar(col = "blue", lty = 2))

# Draw the circle grob
grid.draw(circle)

# Create a rectangular grob
rectangle <- rectGrob(name = "rectangle", x = 0.6, y = 0.6,
                      width = 0.4, height = 0.3,
                      gp = gpar(fill = "lightgreen", col = "darkgreen"))

# Draw the rectangle grob
grid.draw(rectangle)

# Save the file
dev.off()

Output

Lattice Package in R

The Lattice package builds upon the Grid package to create Trellis graphics. These graphics are particularly useful for visualizing relationships between multiple variables under different conditions.

Installing the Lattice Package

The Lattice package can be installed using the following command:

install.packages("lattice")

Lattice provides various graph types, including:

• barchart
• contourplot
• densityplot
• histogram

The general syntax for using these graphs is:

graph_type(formula, data)

• graph_type: Specifies the type of graph to generate.
• formula: Defines the variables or conditional relationships.

To view all functions in the Lattice package, use:

library(help = "lattice")

Example 1: Density Plot

library(lattice)

# Use the built-in mtcars dataset

# Save output as a PNG file
png(file = "density_plot_example.png")

# Create a density plot for the variable 'mpg'
densityplot(~mpg, data = mtcars,
            main = "Density Plot of MPG",
            xlab = "Miles per Gallon")

# Save the file
dev.off()

Output:

Example 2: Histogram

library(lattice)

# Use the built-in ToothGrowth dataset

# Save output as a PNG file
png(file = "histogram_example.png")

# Create a histogram for the variable 'len'
histogram(~len, data = ToothGrowth,
          main = "Histogram of Length",
          xlab = "Length")

# Save the file
dev.off()

Output:

Both the Grid and Lattice packages offer powerful tools for graphical representations in R, making it easier to visualize and analyze data effectively.