Download pdf guide - VSN International

15 Examples 285this is the orange data circ age Tree4 51 2 3Figure 15.12 Trellis plot of trunk circumference for each treeconverted to day of year, measurements were taken in either Spring (April/May)or Autumn (September/October).First we demonstrate the fitting of a cubic spline in ASReml by restricting thedataset to tree 1 only. The model includes the intercept and linear regression oftrunk circumference on age and an additional random term spl(age,7) whichinstructs ASReml to include a random term with a special design matrix with7 − 2 = 5 columns which relate to the vector, δ whose elements δ i , i = 2, . . . , 6are the second differentials of the cubic spline at the knot points. The seconddifferentials of a natural cubic spline are zero at the first and last knot points(Green and Silverman, 1994). The ASReml job isthis is the orange data, for tree 1seq # record number is not usedTree 5age # 118 484 664 1004 1231 1372 1582circseason !L Spring Autumnorange.asd !skip 1 !filter 2 !select 1!SPLINE spl(age,7) 118 484 664 1004 1231 1372 1582!PVAL age 150 200:1500circ ~ mu age !r spl(age,7)predict age