Customizing the Appearance of Spatial Point Patterns in R with spatstat

Understanding the spatstat package in R: A Deep Dive into Plotting Functionality

Introduction to spatstat Package

The spatstat package is a comprehensive library for spatial statistics in R. It provides an efficient and flexible way to analyze and visualize point patterns, which are essential in many fields such as ecology, epidemiology, and geography. In this blog post, we will explore the plotting functionality within the spatstat package, focusing on how to customize the appearance of plots.

The `plot()` Function

The plot() function is a fundamental component of the spatstat package for creating spatial point patterns. It takes in an object of class “ppp” (points pattern) and allows users to specify various parameters to control the visualization.

## Example usage:
swedishpines <- owin(c(0, 96), c(0, 100))
plot(swedishpines)

In this example, we create a rectangular region with zero origin and dimensions of 96x100 units. We then plot this region using the plot() function.

Customizing Plot Appearance

By default, the plot() function does not display axes. To achieve this, you can set the axes argument to TRUE.

## Example usage:
swedishpines <- owin(c(0, 96), c(0, 100))
plot(swedishpines, axes = TRUE)

However, the default plot may not always be aesthetically pleasing. You can customize the appearance of the plot further by using additional arguments such as main, xlab, and ylab.

## Example usage:
swedishpines <- owin(c(0, 96), c(0, 100))
plot(swedishpines, axes = TRUE, main = "Swedish Pines", xlab = "X-axis", ylab = "Y-axis")

Working with Marked Point Patterns

For marked point patterns like ’longleaf’, you can use the plot() function with the axes argument set to TRUE.

## Example usage:
library(spatstat)
longleaf <- rpoints(100, random.type = "uniform", markformat = "none")
plot(longleaf, axes = TRUE)

However, this approach may not provide the most visually appealing results. Instead, you can add axes manually using the axis() function.

## Example usage:
library(spatstat)
longleaf <- rpoints(100, random.type = "uniform", markformat = "none")
plot(longleaf)

# Add x-axis
axis(1, pretty(longleaf$x), pos = 0)

# Add y-axis
axis(2, pretty(longleaf$y), pos = 200)

Customizing Legend Position

The leg.side argument allows you to specify the position of the legend.

## Example usage:
library(spatstat)
longleaf <- rpoints(100, random.type = "uniform", markformat = "none")
plot(longleaf, leg.side = "right", main = "")

# Add x-axis
axis(1, pretty(longleaf$x), pos = 0)

# Add y-axis
axis(2, pretty(longleaf$y), pos = 0)

Conclusion

The spatstat package provides an efficient and flexible way to analyze and visualize point patterns in R. By understanding how to customize the appearance of plots using various arguments and functions, you can effectively communicate your results to others.

In this blog post, we have explored the plotting functionality within the spatstat package, covering topics such as customizing plot appearance, working with marked point patterns, and customizing legend position. Whether you are a seasoned R user or just starting out, the spatstat package offers a wealth of tools for spatial statistics and visualization.