sum_durations() summarizes the duration of visits by person within a timeframe,
and optionally by visit_class of visit. Note:
If for a time frame all rows are NA on the duration column, the summarized duration for that time frame will be NA.
If only some of the rows of a time frame are NA on the duration column, the function will ignore those NA rows.
If there were no visits to a class (i.e., a value of the 'visit_class' column) for a time frame, the summarized duration for that time frame will be zero; if there were visits, but NA on duration, the summarized duration will be NA.
sum_durations(wt, var_duration = NULL, timeframe = NULL, visit_class = NULL)a data.frame with columns panelist_id, column indicating the time unit
(unless timeframe set to NULL), duration_visits indicating the duration of visits
(in seconds, or whatever the unit of the variable specified by var_duration parameter),
and a column for each value of visit_class, if specified.
webtrack data object.
character. Name of the duration variable if already present.
Defaults to NULL, in which case duration will be approximated with
add_duration(wt, cutoff = 300, replace_by = "na", replace_val = NULL)
character. Indicates for what time frame to aggregate visit durations.
Possible values are "date", "week", "month", "year", "wave" or NULL.
If set to "wave", wt must contain a column call wave. Defaults to NULL,
in which case the output contains duration of visits for the entire time.
character. Column that contains a classification of visits.
For each value in this column, the output will have a column indicating the
number of visits belonging to that value. Defaults to NULL.