Various functions to estimate parametric (Gaussian, T -
    distribution, Laplace, Pareto, log-concave distribution and etc.),
    non-parametric mixture models; Perform hypothesis testing, root
    selection and provide treatment for label switching for mixture
    models; Estimate parameters for mixture of regressions, proportion
    varying mixture of regressions and robust mixture of regressions. The
    functions and their corresponding reference paper are as follows:
    KDEEM: Ma, Y., Wang, S., Xu, L. et
    al.(2021)<doi:10.1007/s11749-020-00725-z>; KDEEM.H/KDEEM.LSE: David R.
    Hunter & Derek S. Young (2012)<doi:10.1080/10485252.2011.608430>;
    RM2_mixreg: Yu C, Yao W, Chen K.(2017)<doi:10.1002/cjs.11310>;
    mixlinrb_bi: Xiuqin Bai, Weixin Yao, John E.
    Boyer(2012)<doi:10.1016/j.csda.2012.01.016>; trimmix: N. Neykov, P.
    Filzmoser, R. Dimova, P.
    Neytchev,(2007)<doi:10.1016/j.csda.2006.12.024>; mixlint: Weixin Yao,
    Yan Wei, Chun Yu(2014)<doi:10.1016/j.csda.2013.07.019>; mixreg_Lap:
    Weixing Song, Weixin Yao, Yanru
    Xing(2014)<doi:10.1016/j.csda.2013.06.022>; mixreg_CWRM:
    Garcia-Escudero, L.A., Gordaliza, A., Greselin, F. et al.(2017)
    <doi:10.1007/s11222-021-10061-3>; mphd:Jingjing Wu, Weixin Yao, Sijia
    Xiang (2017)<doi:10.1080/00949655.2017.1318136>;
    EMlogconc/EMlogconcHD: George T. Chang, Guenther
    Walther(2007)<doi:10.1016/j.csda.2007.01.008>;Hypothesis_test:
    Supawadee Wichitchan, Weixin Yao, Guangren
    Yang(2019)<doi:10.1016/j.csda.2018.05.005>; mixscale: Sijia Xiang,
    Weixin Yao, Byungtae Seo(2016)<doi:10.1016/j.csda.2016.06.001>;
    sim/simonestep:Xiang, S., Yao,
    W.(2020)<doi:10.1007/s11634-020-00392-w>; paretomix1: Huang, M., Yao,
    W., Wang, S., and Chen, Y.
    (2018)<doi:10.1111/sjos.12316>;complhfrequency/distlatfrequency:
    Weixin Yao (2015)<doi:10.1080/00949655.2013.859259>; MixReg_Pvary:
    Mian Huang and Weixin Yao (2012)<doi:10.1080/01621459.2012.682541>;
    pfmix: Weixin Yao(2010)<doi:10.1016/j.jspi.2010.02.004>;
    backfitlocal/backfitglobal: Xiang, S., Yao,
    W.(2018)<doi:10.1007/s10463-016-0584-7>;mixbspline: Dziak, J. J., Li,
    R., Tan, X., Shiffman, S., & Shiyko, M. P.
    (2015)<doi:10.1037/met0000048>; root_selection: Supawadee Wichitchan,
    Weixin Yao & Guangren Yang (2019)<doi:10.1080/03610926.2018.1481972>;
    mixbino/mixbinosemi/mixbinosemionestep/mixbinosemifull:J. Cao and W.
    Yao(2012)<https://www3.stat.sinica.edu.tw/sstest/oldpdf/A22n12.pdf>.