cross_corr: Determine cross correlation between two time series for...
In mrc-ide/pika: Evaluate Correlation Between Time Series

This function determines lag at which the cross correlation is highest

cross_corr(
  dat,
  date_var = NULL,
  grp_var,
  x_var,
  y_var,
  max_lag = 20,
  subset_date = NULL
)

`dat`	data frame with columns that correspond to two time series and grouping variable(s)
`date_var`	character string of the column name that corresponds to the date variable date_var must be specified if subset_date is not null.
`grp_var`	character string of column names in dat to be used as grouping variable(s)
`x_var`	primary time series (should be a column in dat)
`y_var`	secondary time series (should be a column in dat)
`max_lag`	integer value of the number of lags to perform cross correlation for
`subset_date`	a character string of the same format as the date variable