When declaring parameters in the parameters block using Dim(),
you can specify a type to automatically apply structural constraints.
These constraints ensure that parameters remain within their valid mathematical
space during estimation.
Details
Standard Types:
"vector","matrix","array": Standard unconstrained containers. Uselowerandupperfor element-wise bounds.
Ordering Constraints:
"ordered": A vector where $x_1 < x_2 < ... < x_K$."positive_ordered": A vector where $0 < x_1 < x_2 < ... < x_K$.
Constrained Vectors:
"simplex": A vector where all elements are >= 0 and sum(x) = 1."centered": A vector of length K where sum(x) = 0. (Estimated using K-1 degrees of freedom).
Correlation and Covariance Matrices:
"corr_matrix": A symmetric, positive-definite correlation matrix (diagonal elements are 1)."cov_matrix": A symmetric, positive-definite covariance matrix."CF_corr": The Cholesky factor of a correlation matrix."CF_cov": The Cholesky factor of a covariance matrix (diagonal elements are positive).
Special Structural Matrices:
"lower_tri": A lower-triangular matrix."positive_lower_tri": A lower-triangular matrix with positive diagonal elements."centered_matrix": A matrix where each column sums to zero."centered_tri": A triangular matrix with column-wise sum-to-zero constraints (often used for identification in factor analysis).