Function disc_batch 

pub fn disc_batch(
    ghi: &[f64],
    solar_zenith: &[f64],
    day_of_year: &[i32],
    pressure: Option<f64>,
) -> (Vec<f64>, Vec<f64>, Vec<f64>)

Batch DISC decomposition. Returns (dni_vec, kt_vec, airmass_vec).