ZTRecur 0.2.0

• Initial release of ZTRecur to CRAN.
• Provides functions for marginal regression and nonparametric estimation of zero-truncated recurrent event data with coarsened censoring times.
• Features C++/Armadillo integration via Rcpp and RcppArmadillo for efficient computation.
• Key exported functions include:
  • birth.interval(): Generates birthdate intervals based on integer ages.
  • nonpara_esti(): Nonparametric estimation of marginal mean and rate functions.
  • plot_nonpar(): Visualization of estimated marginal mean and rate functions.