Van Tassell C P, Van Vleck L D
Roman L. Hruska U.S. Meat Animal Research Center, USDA-ARS, University of Nebraska, Lincoln 68583-0908, USA.
J Anim Sci. 1996 Nov;74(11):2586-97.
A set of FORTRAN programs to implement a multiple-trait Gibbs sampling algorithm for (co)variance component inference in animal models (MTGSAM) was developed. The MTGSAM programs are available to the public. The programs support models with correlated genetic effects and arbitrary numbers of covariates, fixed effects, and independent random effects for each trait. Any combination of missing traits is allowed. The programs were used to estimate variance components for 50 replicates of simulated data. Each replicate consisted of 50 animals of each sex in each of four generations, for 400 animals in each replicate for two traits. For MTGSAM, informative prior distributions for variance components were inverted Wishart random variables with 10 df and means equal to the simulation parameters. A total of 15,000 Gibbs sampling rounds were completed for each replicate, with 2,000 rounds discarded for burn-in. For multiple-trait derivative free restricted maximum likelihood (MTDFREML), starting values for the variance components were the simulation parameters. Averages of posterior mean of variance components estimated using MTGSAM with informative and flat prior distributions for variance components and REML estimates obtained using MTDFREML indicated that all three methods were empirically unbiased. Correlations between estimates from MTGSAM using flat priors and MTDFREML all exceeded .99.
开发了一组FORTRAN程序，用于实现动物模型中（协）方差成分推断的多性状吉布斯采样算法（MTGSAM）。MTGSAM程序可供公众使用。这些程序支持具有相关遗传效应以及每个性状具有任意数量的协变量、固定效应和独立随机效应的模型。允许任何缺失性状的组合。这些程序用于估计模拟数据50次重复的方差成分。每次重复包括四代中每代各50只每种性别的动物，即每次重复针对两个性状有400只动物。对于MTGSAM，方差成分的信息先验分布是自由度为10且均值等于模拟参数的逆威沙特随机变量。每次重复完成总共15,000次吉布斯采样轮次，舍弃前2,000轮次用于预烧。对于多性状无导数限制最大似然法（MTDFREML），方差成分的初始值为模拟参数。使用具有信息性和平坦先验分布的MTGSAM估计的方差成分后验均值的平均值以及使用MTDFREML获得的REML估计表明，所有三种方法在经验上都是无偏的。使用平坦先验的MTGSAM估计与MTDFREML估计之间的相关性均超过0.99。
