Tree Height Response Calibration for Swedish Forests R package THREC version 1.0.0 A tool that allows users to estimate tree height in the long-term forest experiments in Sweden. It utilizes the multilevel nonlinear mixed-effect height models developed for the forest experiments and consists of four functions for the main species, other conifer species, and other broadleaves. Each function within the system returns a data frame that includes the input data and the estimated heights for any missing values. Ogana et al. (2023) <doi:10.1016/j.foreco.2023.120843>\n Arias-Rodil et al. (2015) <doi:10.1371/JOURNAL.PONE.0143521>. Software Depends: R (>= 3.5.0) Imports: Matrix, magic, Deriv (>= 1.0), dplyr (>= 1.0.0), tidyr (>= 1.1.0) Friday Nwabueze Ogana <ogana_fry@yahoo.com> Comprehensive R Archive Network (CRAN) Friday Nwabueze Ogana [aut, cre] (ORCID: <https://orcid.org/0000-0002-8388-204X>), Manuel Arias-Rodil [aut] GPL (>= 3) 2023-12-19 application/tgz https://CRAN.R-project.org/package=THREC doi:10.32614/CRAN.package.THREC