eventCounts function

Tabulate vector of dates by specified time event

For example, dates may be dates of plane crashes. For purposes of analysis, this function tabulates number of crash events per event of time, for each successive specified event.

eventCounts(data, dateCol="Date", from = NULL, to = NULL,
          by = "1 month", categoryCol=NULL, takeOnly=NULL, prefix="n_")

Arguments

• data: Data frame that should include any columns whose names appear in other function arguments.
• dateCol: Name of column that holds vector of dates
• from: Starting date. If NULL set to first date given. If supplied, any rows earlier than from will be omitted. Similarly, rows later than any supplied date to will be omitted.
• to: Final date, for which numbers of events are to be tallied. If NULL set to final date given.
• by: Time event to be used; e.g. "1 day", or "1 week", or "4 weeks", or "1 month", or "1 quarter", or "1 year", or "10 years".
• categoryCol: If not NULL create one column of counts for each level (or if not a factor, unique value).
• takeOnly: If not NULL, a charater string that when deparsed and executed will return a vector of logicals.
• prefix: If categoryCol is not NULL, a prefix for the names of the columns of counts. Otherwise (categoryCol=NULL) a name for the column of counts.

Returns

A data frame, with columns Date (the first day of the event for which events are given), and other column(s) that hols counts of events.

Author(s)

John Maindonald

See Also

cut

Examples

crashDate <- as.Date(c("1908-09-17","1912-07-12","1913-08-06",
                       "1913-09-09","1913-10-17"))
df <- data.frame(date=crashDate)
byYears <- eventCounts(data=df, dateCol="date",
                       from=as.Date("1908-01-01"),
                       by="1 year")