isStationary {uGMAR}R Documentation

DEPRECATED, USE is_stationary INSTEAD! Check the stationary condition of specified GMAR, StMAR, or G-StMAR model.

Description

isStationary checks the stationarity condition of the specified GMAR, StMAR, or G-StMAR model. DEPRECATED, USE is_stationary INSTEAD!

Usage

isStationary(
  p,
  M,
  params,
  model = c("GMAR", "StMAR", "G-StMAR"),
  restricted = FALSE,
  constraints = NULL
)

Arguments

p

a positive integer specifying the autoregressive order of the model.

M
For GMAR and StMAR models:

a positive integer specifying the number of mixture components.

For G-StMAR models:

a size (2x1) integer vector specifying the number of GMAR type components M1 in the first element and StMAR type components M2 in the second element. The total number of mixture components is M=M1+M2.

params

a real valued parameter vector specifying the model.

For non-restricted models:

Size (M(p+3)+MM11x1)(M(p+3)+M-M1-1x1) vector θ\theta==(υ1\upsilon_{1},...,,...,υM\upsilon_{M}, α1,...,αM1,\alpha_{1},...,\alpha_{M-1},ν\nu) where

  • υm\upsilon_{m}=(ϕm,0,=(\phi_{m,0},ϕm\phi_{m},,σm2)\sigma_{m}^2)

  • ϕm\phi_{m}=(ϕm,1,...,ϕm,p),m=1,...,M=(\phi_{m,1},...,\phi_{m,p}), m=1,...,M

  • ν\nu=(νM1+1,...,νM)=(\nu_{M1+1},...,\nu_{M})

  • M1M1 is the number of GMAR type regimes.

In the GMAR model, M1=MM1=M and the parameter ν\nu dropped. In the StMAR model, M1=0M1=0.

If the model imposes linear constraints on the autoregressive parameters: Replace the vectors ϕm\phi_{m} with the vectors ψm\psi_{m} that satisfy ϕm\phi_{m}==CmψmC_{m}\psi_{m} (see the argument constraints).

For restricted models:

Size (3M+MM1+p1x1)(3M+M-M1+p-1x1) vector θ\theta=(ϕ1,0,...,ϕM,0,=(\phi_{1,0},...,\phi_{M,0},ϕ\phi,, σ12,...,σM2,\sigma_{1}^2,...,\sigma_{M}^2,α1,...,αM1,\alpha_{1},...,\alpha_{M-1},ν\nu), where ϕ\phi=(ϕ1,...,ϕp)(\phi_{1},...,\phi_{p}) contains the AR coefficients, which are common for all regimes.

If the model imposes linear constraints on the autoregressive parameters: Replace the vector ϕ\phi with the vector ψ\psi that satisfies ϕ\phi==CψC\psi (see the argument constraints).

Symbol ϕ\phi denotes an AR coefficient, σ2\sigma^2 a variance, α\alpha a mixing weight, and ν\nu a degrees of freedom parameter. If parametrization=="mean", just replace each intercept term ϕm,0\phi_{m,0} with the regimewise mean μm=ϕm,0/(1ϕi,m)\mu_m = \phi_{m,0}/(1-\sum\phi_{i,m}). In the G-StMAR model, the first M1 components are GMAR type and the rest M2 components are StMAR type. Note that in the case M=1, the mixing weight parameters α\alpha are dropped, and in the case of StMAR or G-StMAR model, the degrees of freedom parameters ν\nu have to be larger than 22.

model

is "GMAR", "StMAR", or "G-StMAR" model considered? In the G-StMAR model, the first M1 components are GMAR type and the rest M2 components are StMAR type.

restricted

a logical argument stating whether the AR coefficients ϕm,1,...,ϕm,p\phi_{m,1},...,\phi_{m,p} are restricted to be the same for all regimes.

constraints

specifies linear constraints imposed to each regime's autoregressive parameters separately.

For non-restricted models:

a list of size (pxqm)(pxq_{m}) constraint matrices CmC_{m} of full column rank satisfying ϕm\phi_{m}==CmψmC_{m}\psi_{m} for all m=1,...,Mm=1,...,M, where ϕm\phi_{m}=(ϕm,1,...,ϕm,p)=(\phi_{m,1},...,\phi_{m,p}) and ψm\psi_{m}=(ψm,1,...,ψm,qm)=(\psi_{m,1},...,\psi_{m,q_{m}}).

For restricted models:

a size (pxq)(pxq) constraint matrix CC of full column rank satisfying ϕ\phi==CψC\psi, where ϕ\phi=(ϕ1,...,ϕp)=(\phi_{1},...,\phi_{p}) and ψ\psi=ψ1,...,ψq=\psi_{1},...,\psi_{q}.

The symbol ϕ\phi denotes an AR coefficient. Note that regardless of any constraints, the autoregressive order is always p for all regimes. Ignore or set to NULL if applying linear constraints is not desired.

Details

DEPRECATED, USE is_stationary INSTEAD! This function falsely returns FALSE for stationary models when the parameter is extremely close to the boundary of the stationarity region.

Value

Returns TRUE or FALSE accordingly.

References


[Package uGMAR version 3.5.0 Index]