# Example Mx Script

Multivariate ACE Twin Model


! Mx ACE script for twin data

#define nvar 3

Group1: Defines Matrices
Data Calc NGroups=4

Begin Matrices;
X Lower nvar nvar free    ! genetic structure
Y Lower nvar nvar free    ! shared environment
Z Lower nvar nvar free    ! non-shared environment

H Full 1 1
I Iden 4 4
End Matrices;

Matrix H .5

Begin Algebra;
A= X*X';   ! genetic covariance matrix
C= Y*Y';   ! environmental covariance matrix
E= Z*Z';   ! nonshared environmental covariance matrix
End Algebra;

Start 0   X 1 1 to X nvar nvar
Start 0   Y 1 1 to Y nvar nvar
Start 1.7 Z 1 1 to Z nvar nvar

End

Group2: MZ twin pairs
Data NInput_vars=6 NObservations=1500
CMatrix
4.24756
-.280441  3.39532
2.01213    .05206    2.95854
3.2865    -.243047   2.01504   4.39321
-.210246  2.38388     .096846  -.202754  3.42946
2.02091    .050704   2.44859   2.02949    .114946  2.86705

Labels x1 y1 z1 x2 y2 z2

Matrices= Group 1

Covariances A + C + E  |    A + C  _
A + C    |  A + C + E /

Option RS
End

Group3: DZ twin pairs
Data NInput_vars=6 NObservations=2000
CMatrix
4.35496
-.354591  3.68418
2.04503    .097915  3.17886
2.12497    .329648  1.41837   4.15677
.241837  1.64101    .430632  -.216949  3.43144
1.34426    .501343  1.70592   2.01647    .139561   3.12658

Labels x1 y1 z1 x2 y2 z2

Matrices= Group 1

Covariances A + C + E  |   H@A + C  _
H@A + C   |  A + C + E /

Option RS
End

Group4: Standardised solution
Calculation

Matrices = group 1

Begin Algebra;

! phenotypic covariance matrix
P = A + C + E;

! diagonal matrix of phenotypic
! standard deviations
D = \sqrt(\v2d(\d2v(P)));

! phenotypically standardised genetic
!  covariance matrix
T = D~ * A * D~;

! phenotypically standardised shared
!  environmental covariance matrix
U = D~ * C * D~;

! phenotypically standardised
!  nonshared environmental covariance matrix
V = D~ * E * D~;

! Genetic correlation matrix
G = \stnd(T);

! Shared environmental correlation matrix
S = \stnd(U);

! Nonshared environmental correlation matrix
N = \stnd(V);

End Algebra;

End