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Exercise

Temporal pattern of bigfoot sightings

Having established that there is some spatial clustering going on, you need to explore the temporal behavior. Are the number of sightings increasing? Decreasing? Does the rate vary over the course of a year ("seasonality")? Does the spatial pattern change much over the course of a year?

The base R hist() function has a method for dates that lets you specify a time unit for the breaks. You pass a string to the breaks argument, such as "days", "weeks", "months", "quarters" or "years".

Instructions
100 XP

The sasq object is loaded for you.

  • Create a histogram of the date aggregated by year.
    • The first argument is the vector of date marks.
    • The second argument is a string specifying the time period.
  • Make a table of the months of sightings and plot to see if there's an overall annual pattern.
  • Split the points by the calendar month, assigning the result to sasq_by_month.
    • Call split().
    • Pass it the sasquatch point pattern, a string naming the mark to split on, and un = TRUE to return unmarked point patterns.
  • Plot sasq_by_month to produce 12 maps.
  • Plot the density() of sasq_by_month to draw 12 density maps.