MatrixTDistribution
MatrixTDistribution[Σrow,Σcol,ν]
represents zero mean matrix distribution with row covariance matrix Σrow, column covariance matrix Σcol, and degrees of freedom parameter ν.
MatrixTDistribution[μ,Σrow,Σcol,ν]
represents matrix distribution with mean matrix μ.
Details
- The probability density for a matrix of dimensions in a matrix distribution is proportional to with an identity matrix of length .
- MatrixTDistribution[Σrow,Σcol,ν] is the distribution of MatrixNormalDistribution[Σ,Σcol] with sampled from InverseWishartMatrixDistribution[ν+n-1,Σrow].
- MatrixTDistribution[μ,c Σrow,c-1 Σcol,ν] has the same distribution as MatrixTDistribution[μ,Σrow,Σcol,ν] for any positive real constant c.
- The covariance matrices Σrow and Σcol can be any symmetric positive definite matrices of real numbers of dimensions {n,n} and {m,m}, respectively. The degrees of freedom parameter ν can be any positive number, and the mean matrix μ can be any matrix of real numbers of dimensions {n,m}.
- MatrixTDistribution can be used with such functions as MatrixPropertyDistribution, EstimatedDistribution, and RandomVariate.
Examples
open allclose allScope (6)
Generate a single pseudorandom matrix:
Generate a single pseudorandom matrix with nonzero mean:
Generate a set of pseudorandom matrices:
Distribution parameters estimation:
Estimate the distribution parameters from sample data:
Compare LogLikelihood for both distributions:
Properties & Relations (4)
Matrix t distribution is defined up to a positive multiplicative constant:
Equivalent distribution with row and column scale matrices multiplied and divided by a positive constant:
Compute the PDF of the distributions at a random point:
MatrixTDistribution[Σrow,Σcol,ν] is a parameter mixture of MatrixNormalDistribution[Σ,Σcol] with following InverseWishartMatrixDistribution[ν+n-1,Σrow]:
Create a sample following the parameter mixture of MatrixNormalDistribution with InverseWishartMatrixDistribution:
Fit the sample data to MatrixTDistribution:
Compute log-likelihood ratio statistic against the appropriate MatrixTDistribution
Log-likelihood ratio follows ChiSquareDistribution with the parameter equal to the number of degrees of freedom:
Compute the -value of log-likelihood ratio test:
For matrix sampled from matrix distribution, the expression follows Student distribution for any nonzero vectors and with lengths that match with the dimension of :
Use MatrixPropertyDistribution to sample values of the expression :
Check agreement with the expected distribution:
For matrix sampled from matrix distribution, follows multivariate distribution for any nonzero vector with length that matches with the number of columns of :
Use MatrixPropertyDistribution to sample values of :
Possible Issues (1)
Matrix distribution is defined up to a multiplicative scaling constant. The estimated parameters may not be close to the ones that specify the underlying distribution:
Sample from the matrix distribution:
Compare the estimated scale parameters with the ones of the underlying distribution:
Kronecker products of the scale matrices are close to each other:
The LogLikelihood of the distributions indicate that the estimate is good:
Text
Wolfram Research (2015), MatrixTDistribution, Wolfram Language function, https://reference.wolfram.com/language/ref/MatrixTDistribution.html (updated 2017).
CMS
Wolfram Language. 2015. "MatrixTDistribution." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2017. https://reference.wolfram.com/language/ref/MatrixTDistribution.html.
APA
Wolfram Language. (2015). MatrixTDistribution. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/MatrixTDistribution.html