Returns the age-interpolated median of the GCDG references (Weber et al, 2019). The working range is 0-4 years. This function is used to set prior mean under keys "gcdg" and "gsed1912".
count_mu_gcdg(t)
Arguments
t: Decimal age, numeric vector
Returns
A vector of length length(t) with the median of the GCDG references.