We provide a rich collection of linear and nonlinear dimension reduction techniques implemented using 'RcppArmadillo'. The question on what we should use as the target dimension is addressed by intrinsic dimension estimation methods introduced as well. For more details on dimensionality techniques, see the paper by Ma and Zhu (2013) <doi:10.1111/j.1751-5823.2012.00182.x> if you are interested in statistical approach, or Engel, Huttenberger, and Hamann (2012) <doi:10.4230/OASIcs.VLUDS.2011.135> ...