! 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 free     !nonadditive/dominance genetic effects
X LOwer 1 1 free     !additive genetic effects
Y LOwer 1 1 fixed    !shared environmental effects
Z LOwer 1 1 free     !unique environmental effects
H FUll 1 1           
Q FUll 1 1
End Matrices:
Matrix H 
.5
Matrix Q
.25
Begin Algebra;
A = X*X' ;
D = W*W' ;
C = Y*Y' ;
E = Z*Z' ;
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 Vp
End

Group 2: Young Female MZ Twins
DAta_Group NInput=2 NObs=534
LAbels BMI_T1 BMI_T2
CMatrix SYmmetric
.7247
.5891 .7915
Matrices = Group 1
Covarinace A+C+D+E | A+C+D _
           A+C+D   | A+C+D+E /
Options RSiduals NDecimals=3
End

Group 3: Young Female DZ Twins
DAta_Group NInput=2 NObs=328
LAbels BMI_T1 BMI_T2
CMatrix SYmmetric
.7786
.2461 .8365
Matrices = Group 1
COvarinace A+C+D+E   | H@A+C+Q@D _
           H@A+C+Q@D | A+C+D+E /
Interval A 1 1 1 D 1 1 1 E 1 1 1   !computes 95% CIs
Options RSiduals ND=3
Options multiple issat             !multiple model fit option
End

!AE Model (drops non-additive genetic effects)
Drop 1
End

!E-Only Model (drops all genetic effects)
Drop 2
End