Creating a uniform point pattern with spatstat

A Poisson point process creates events according to a Poisson distribution with an intensity parameter specifying the expected events per unit area. The total number of events generated is a single number from a Poisson distribution, so multiple realizations of the same process can easily have different numbers of events.

In the previous exercise you used a set of 300 events scattered uniformly within a circle. If you repeated the generation of the events again you will still have 300 of them, but in different locations. The dataset of exactly 300 points is from a Poisson point process conditioned on the total being 300.

The spatstat package can generate Poisson spatial processes with the rpoispp() function given an intensity and a window, that are not conditioned on the total.

Just as the random number generator functions in R start with an "r", most of the random point-pattern functions in spatstat start with an "r".

The area() function of spatstat will compute the area of a window such as a disc.

Create a disc of radius 10, assigning the result to disc10.
To generate approximately 500 points in a disc of radius 10, set lambda to 500 divided by the area() of the disc. Assign the result to lambda.
Generate a random Poisson point pattern with intensity lambda and window disc10, assigning the result to ppois. Do you get about 500 points?
Plot the Poisson point pattern by calling plot() on ppois.

Exercise

Creating a uniform point pattern with spatstat

Instructions