用Mixed和Nlmixed过程建立混合生长模型

Establishment of Tree Height Growth Model Based on Mixed and Nlmixed of SAS

本文用5块不同密度样地的树高生长资料,根据线性和非线性混合模型理论,利用SAS的Mixed过程和Nlmixed过程,分别拟合线性混合模型和非线性混合树高生长模型。根据预测值和固定效应同时绘制出不同密度下的高生长曲线和平均高生长曲线,充分显示了混合模型的优势,即它可以同时反映总体的平均变化趋势和个体之间的差异。

Based on the data of height growth in 5 plots with different densities,mixed and nlmixed of SAS were used to fit the linear and non-linear mixed models of tree height growth respectively.The height growth curve and mean height growth curve under different densities were drawn according to calculated value and fixed effect value,which showed the advantages of the mixed model,i.e.it could reflect the mean variation trend on the 5 plots and the differences among individuals at the same time.