| arch {vars} | R Documentation |
ARCH-LM testDescriptionThis function computes univariate and multivariate ARCH-LM tests for aVAR(p).
Usagearch(x, lags.single = 16, lags.multi = 5, multivariate.only = TRUE)
Arguments
| x | Object of class ‘varest’; generated byVAR(), or an object of class ‘vec2var’; generated byvec2var(). |
| lags.single | An integer specifying the lags to be used for theunivariate ARCH statistics. |
| lags.multi | An integer specifying the lags to be used for themultivariate ARCH statistic. |
| multivariate.only | If TRUE (the default), onlythe multivariate test statistic is computed. |
DetailsThe multivariate ARCH-LM test is based on the following regression(the univariate test can be considered as special case of theexhibtion below and is skipped):
vech(hat{u}_t hat{u}_t') = β_0 + B_1vech(hat{u}_{t-1} hat{u}_{t-1}') + ... + B_qvech(hat{u}_{t-q} hat{u}_{t-q}' + v_t)
whereby
v_t assigns a spherical error process and
vech is the column-stacking operator for symmetric matricesthat stacks the columns from the main diagonal on downwards. Thedimension of
β_0 is
frac{1}{2}K(K +1) and forthe coefficient matrices
B_i with
i=1, ..., q,
frac{1}{2}K(K +1) times frac{1}{2}K(K +1). The nullhypothesis is:
H_0 := B_1 = B_2 = ... = B_q = 0 and thealternative is:
H_1: B_1 neq 0 or B_2 neq 0 or ... B_q neq0.The test statistic is:
VARCH_{LM}(q) = frac{1}{2}T K (K + 1)R_m^2 quad ,
with
R_m^2 = 1 - frac{2}{K(K+1)}tr(hat{Omega} hat{Omega}_0^{-1})quad ,
and
hat{Omega} assigns the covariance matrix of the abovedefined regression model. This test statistic is distributed as
chi^2(qK^2(K+1)^2/4).
ValueA list with class attribute ‘varcheck’ holding thefollowing elements:
| resid | A matrix with the residuals of the VAR. |
| arch.uni | A list with objects of class ‘htest’containing the univariate ARCH-LM tests per equation. This elementis only returned if multivariate.only = FALSE is set. |
| arch.mul | An object with class attribute ‘htest’containing the multivariate ARCH-LM statistic. |
Author(s)Bernhard Pfaff
ReferencesDoornik, J. A. and D. F. Hendry (1997),
Modelling DynamicSystems Using PcFiml 9.0 for Windows, International ThomsonBusiness Press, London.
Engle, R. F. (1982), Autoregressive conditional heteroscedasticitywith estimates of the variance of United Kingdom inflation,
Econometrica,
50: 987-1007.
Hamilton, J. (1994),
Time Series Analysis, PrincetonUniversity Press, Princeton.
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