get_error_triphasic: Evaluate error metric between data and model prediction
In ushr: Understanding Suppression of HIV

For a given parameter set, this function computes the predicted viral load curve and evaluates the error metric between the prediction and observed data (to be passed to optim).

1 2	get_error_triphasic(params, param_names, free_param_index, data, inv_param_transform_fn)

`params`	named vector of the parameters from which the model prediction should be generated.
`param_names`	names of parameter vector.
`free_param_index`	logical TRUE/FALSE vector indicating whether the parameters A, delta, A_b, delta_b, B, gamma are to be recovered. This should be c(TRUE, TRUE, TRUE, TRUE, TRUE, TRUE) for the triphasic model.
`data`	dataframe with columns for the subject's viral load measurements ('vl'), and timing of sampling ('time').
`inv_param_transform_fn`	list of transformation functions to be used when back-transforming the transformed parameters. Should be the inverse of the forward transformation functions. Defaults to exponential.