# GARCHM_CHECK - Check parameters' values for model stability

Examines the model's parameters for stability constraints (e.g. stationary, positive variance, etc.).

## Syntax

GARCHM_CHECK(mean, lambda, alphas, betas, innovation, v)
mean
is the GARCH-M model mean (i.e. mu).
lambda
is the volatility coefficient for the mean. In finance, lambda is referenced as the risk premium.
alphas
are the parameters of the ARCH(p) component model (starting with the lowest lag).
betas
are the parameters of the GARCH(q) component model (starting with the lowest lag).
innovation
is the probability distribution model for the innovations/residuals (1=Gaussian (default), 2=t-Distribution, 3=GED).
value Description
1 Gaussian or Normal Distribution (default)
2 Student's t-Distribution
3 Generalized Error Distribution (GED)
v
is the shape parameter (or degrees of freedom) of the innovations/residuals probability distribution function.

## Remarks

1. The underlying model is described here.
2. The time series is homogeneous or equally spaced.
3. To ensure positive conditional variance and finite unconditional variance, the model's cofficient must meet the following:
• $\alpha_o \gt 0$
• $\alpha_i \geq 0$
• $\beta_i \geq 0$
• $\sum_{i=1}^{max(p,q}(\alpha_i+\beta_i) \lt 1$
4. The number of parameters in the input argument - alpha - determines the order of the ARCH component model.
5. The number of parameters in the input argument - beta - determines the order of the GARCH component model.

## Examples

Example 1:

1
2
3
4
5
6
A B
GARCHM(1,1)
Mean -0.076
Lambda 0.145
Alpha_0 0.593
Alpha_1 0.000
Beta_1 0.403

Formula Description (Result)
=GARCHM_CHECK($B$2,$B$3,$B$4:$B$5,$B$6) The model is stable? (1)