! MX EXAMPLE: Traditional Path Coefficients ACE/ADE Model
!
! BMI data from Australian Twins (Martin & Jardine, 1986)
! BMI estimated as 7 x log(wt/ht*ht),
! Where wt is weight in kg, ht is height in meters
!
! This univariate example uses only female twin data from young cohort

#NGroups 3

Group 1: define model parameters and compute squared quantities
Calculation_Group
Begin Matrices;
W LOwer 1 1 fixed    !nonadditive/dominance genetic effects
X LOwer 1 1 free      !additive genetic effects
Y LOwer 1 1 free      !shared environmental effects
Z LOwer 1 1 free      !unique environmental effects
H FUll 1 1                     !fixed by default when not specified
Q FUll 1 1
End Matrices:
Matrix H             !fixes value in matrix H to .5
.5             
Matrix Q             !fixes value in matrix Q to .25
.25
Begin Algebra;
A = X*X' ;           !A = a**2 = additive genetic variance component
D = W*W' ;         !D = d**2 = nonadditive genetic variance component
C = Y*Y' ;           !C = c**2 = shared env variance component
E = Z*Z' ;            !E = e**2 = nonshared env variance componet
End Algebra;
Label Row W dom_gen  !labels for output
Label Row X add_gen
Label Row Y shr-env
Label Row Z uni-env
Label Row D dom_gen
Label Row A add_gen
Label Row C shr-env
Label Row E uni-env
Start .5 All         !3 x .5squared = .75, roughly the observed Vp
End

Group 2: Young Female MZ Twins
DAta_Group NInput=2 NObs=534
LAbels BMI_T1 BMI_T2
CMatrix SYmmetric                             !input/observed MZ cov matrix
.7247
.5891 .7915
Matrices = Group 1
Covarinace A+C+D+E | A+C+D _    !expected MZ cov matrix based on model
           A+C+D   | A+C+D+E /
Options RSiduals ND=3                     !options for output
End

Group 3: Young Female DZ Twins
DAta_Group NInput=2 NObs=328
LAbels BMI_T1 BMI_T2
CMatrix SYmmetric                                              !observed DZ cov matrix
.7786
.2461 .8365
Matrices = Group 1
COvarinace A+C+D+E   | H@A+C+Q@D _   !expected DZ cov matrix
           H@A+C+Q@D | A+C+D+E /
Options RSiduals ND=3
End