Example Mx Script

! Mx ACE script for twin data

#define nvar 1

Group1: Defines Matrices
Calc NGroups=4

	Begin Matrices;
	                                  ! path co-efficients
		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

	End Matrices;

	Matrix H .5

	Begin Algebra;
	                   ! variance matrices
		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 1.5 Z 1 1 to Z nvar nvar

End


Group2: MZ twin pairs
Data NInput_vars=2 NObservations=1500
     CMatrix 
	2.12
	1.67	2.08

     Labels trait1 trait2 

     Matrices= Group 1

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

     Option RS
End


Group3: DZ twin pairs
Data NInput_vars=2 NObservations=2000
     CMatrix 
	1.98
	1.25	2.06

     Labels trait1 trait2 

     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