Fit cosinor model for subset of data. Called by main 'kronos' function.
pairwise_cosinor_model(data, formula, time, verbose)
input data
A formula. Use the time
function to designate which variable represents time.
A string. Should be the column name containing the time values.
A boolean. Toggles whether to print diagnostic information while running. Useful for debugging errors on large data sets.