Function rgsl::fit::linear_est

pub fn linear_est(
    x: f64,
    c0: f64,
    c1: f64,
    cov00: f64,
    cov01: f64,
    cov11: f64
) -> Result<(f64, f64), Value>

This function uses the best-fit linear regression coefficients c0, c1 and their covariance cov00, cov01, cov11 to compute the fitted function y and its standard deviation y_err for the model Y = c_0 + c_1 X at the point x.

Returns (y, y_err).