| test.BHEP | R Documentation |
Performs the BHEP test of multivariate normality of Henze and Wagner
(1997), with tuning parameter a. Critical values and p-values are obtained
by Monte Carlo simulation or by fitting a Pearson or Johnson distribution
to the first four moments of the limiting null distribution.
test.BHEP(
data,
a = 1,
MC.rep = 10000,
alpha = 0.05,
cv.method = c("MC", "Pearson", "Johnson")
)
data |
A numeric |
a |
Positive, finite tuning parameter; corresponds to |
MC.rep |
Positive integer giving the number of Monte Carlo
replications. Used only when |
alpha |
Significance level, strictly between zero and one. |
cv.method |
Method used to approximate the critical value:
|
The test statistic is
BHEP_{n,\beta} = \frac{1}{n}\sum_{j,k=1}^n
\exp\left(-\frac{\beta^2\|Y_{n,j}-Y_{n,k}\|^2}{2}\right)
- \frac{2}{(1+\beta^2)^{d/2}}\sum_{j=1}^n
\exp\left(-\frac{\beta^2\|Y_{n,j}\|^2}{2(1+\beta^2)}\right)
+ \frac{n}{(1+2\beta^2)^{d/2}}.
Here \beta=a,
Y_{n,j}=S_n^{-1/2}(X_j-\overline{X}_n), and
S_n=n^{-1}\sum_{j=1}^n
(X_j-\overline{X}_n)(X_j-\overline{X}_n)^\top.
With cv.method = "MC", cv.quan simulates the null
distribution at the observed sample size n and dimension d,
using MC.rep replications. The same simulated statistics are used for the critical value and the
Monte Carlo p-value
p_{MC}=\frac{1+\sum_{b=1}^{B}\mathbf{1}\{T_b\ge T_{obs}\}}{B+1},
where B is MC.rep. The critical value retains
the order-statistic convention of cv.quan, and Decision
remains Test.value > cv. Because the Monte Carlo p-value is discrete
and uses the plus-one correction, this decision can differ from
pvalue <= alpha near the cutoff.
With cv.method = "Pearson" or "Johnson", the critical
value is obtained from a moment-based approximation to the limiting null
distribution T_\beta(d). Let \kappa_r denote its cumulants.
The first three cumulants are given by Henze and Wagner (1997), and the
fourth by Theorem 3.2 and Appendix A of Ebner and Henze's announced
manuscript. The mean, variance, skewness and ordinary kurtosis are
\mu=\kappa_1,\quad \sigma^2=\kappa_2,\quad
\gamma_1=\kappa_3/\kappa_2^{3/2},\quad
\beta_2=3+\kappa_4/\kappa_2^2.
In particular, the fourth central moment is
\mu_4=\kappa_4+3\kappa_2^2; it is not the fourth cumulant.
An object of class "mnt", with components:
TestName of the test.
paramValue of the tuning parameter.
Test.valueValue of the test statistic.
cvApproximated upper 1-\alpha critical value.
DecisionTRUE if Test.value > cv, so the
null hypothesis is rejected at the chosen significance level.
cv.methodCritical-value method actually used.
pvalueUpper-tail p-value computed using the selected method. The Pearson and Johnson p-values are asymptotic approximations.
Henze, N. and Wagner, T. (1997). A new approach to the BHEP tests for multivariate normality. Journal of Multivariate Analysis, 62, 1–23. \Sexpr[results=rd]{tools:::Rd_expr_doi("10.1006/jmva.1997.1684")}.
Ebner, B. and Henze, N. Four-Moment Approximations and Fast p-Values for BHEP Tests of Multivariate Normality. Supplied manuscript ‘BHEP_fourth_moment.pdf’, Theorem 3.2 and Appendix A.
BHEP, cv.quan
set.seed(123)
x <- matrix(rnorm(100), ncol = 2)
test.BHEP(x, MC.rep = 500)
if (requireNamespace("PearsonDS", quietly = TRUE)) {
test.BHEP(x, cv.method = "Pearson")
}
if (requireNamespace("SuppDists", quietly = TRUE)) {
test.BHEP(x, cv.method = "Johnson")
}
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