Function calculate_auc_at_times 

pub fn calculate_auc_at_times(
    dense_times: &[f64],
    dense_predictions: &[f64],
    target_times: &[f64],
) -> Vec<f64>

Calculate cumulative AUC at target times using trapezoidal rule

Takes dense concentration predictions and calculates cumulative AUC from the first time point. AUC values at target observation times are extracted and returned.

Arguments

• dense_times - Dense time grid (must include all target_times)
• dense_predictions - Concentration predictions at dense_times
• target_times - Observation times where AUC should be extracted

Returns

Vector of AUC values at target_times