Description Usage Arguments Details Value Author(s) References See Also Examples
Implements first-order and higher-order likelihood methods for inference in meta-analysis and meta-regression models, as described in Guolo (2012). Higher-order asymptotics refer to the higher-order adjustment to the log-likelihood ratio statistic for inference on a scalar component of interest as proposed by Skovgaard (1996). See Guolo and Varin (2012) for illustrative examples about the usage of metaLik package.
1 |
formula |
an object of class |
data |
an optional data frame, list or environment (or object
coercible by |
subset |
an optional vector specifying a subset of observations to be used in the fitting process. |
contrasts |
an optional list. See the contrasts.arg of |
offset |
this can be used to specify an a priori known component to be included in the linear predictor during fitting. This should be |
sigma2 |
a vector of within-study estimated variances. The length of the vector must be the same of the number of studies. |
weights |
a vector of the inverse of within-study estimated variances. The length of the vector must be the same of the number of studies. If |
Models for metaLik.fit
are specified simbolically. A typical model has the form y ~ x1 + ... + xJ
, where y
is the continuous response term and xj
is the j-th covariate available at the aggregated meta-analysis level for each study. The case of no covariates corresponds to the classical meta-analysis model specified as y~1
.
Within-study variances are specified through sigma2
: the rare case of equal within-study variances implies Skovgaard's adjustment reaching a third-order accuracy.
DerSimonian and Laird estimates (DerSimonian and Laird, 1986) are also supplied.
An object of class "metaLik"
with the following components:
y |
the y vector used. |
X |
the model matrix used. |
fitted.values |
the fitted values. |
sigma2 |
the within-study variances used. |
K |
the number of studies. |
mle |
the vector of the maximum likelihood parameter estimates. |
vcov |
the variance-covariance matrix of the parameter estimates. |
max.lik |
the maximum log-likelihood value. |
beta.mle |
the vector of fixed-effects parameters estimated according to maximum likelihood. |
tau2.mle |
the maximum likelihood estimate of τ^2. |
DL |
the vector of fixed-effects parameters estimated according to DerSimonian and Laird's pproach. |
tau2.DL |
the method of moments estimate of the heterogeneity parameter τ^2. |
vcov.DL |
the variance-covariance matrix of the DL parameter estimates. |
call |
the matched call. |
formula |
the |
terms |
the |
offset |
the offset used. |
contrasts |
(only where relevant) the |
xlevels |
(only where relevant) a record of the levels of the factors used in fitting. |
model |
the model frame used. |
Generic functions coefficients
, vcov
, logLik
, fitted
, residuals
can be used to extract fitted model quantities.
Annamaria Guolo and Cristiano Varin.
DerSimonian, R. and Laird, N. (1986). Meta-Analysis in Clinical Trials. Controlled Clinical Trials 7, 177–188.
Guolo, A. (2012). Higher-Order Likelihood Inference in Meta-Analysis and Meta-Regression. Statistics in Medicine 31, 313–327.
Guolo, A. and Varin, C. (2012). The R Package metaLik for Likelihood Inference in Meta-Analysis. Journal of Statistical Software 50 (7), 1–14. http://www.jstatsoft.org/v50/i07/.
Skovgaard, I. M. (1996). An Explicit Large-Deviation Approximation to One-Parameter Tests. Bernoulli 2, 145–165.
Function summary.metaLik
for summaries.
Function test.metaLik
for hypothesis testing.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | ## meta-analysis
data(education)
m <- metaLik(y~1, data=education, sigma2=sigma2)
summary(m)
## meta-analysis
data(albumin)
m <- metaLik(y~1, data=albumin, sigma2=sigma2)
summary(m)
## meta-regression
data(vaccine)
m <- metaLik(y~latitude, data=vaccine, sigma2=sigma2)
summary(m)
## meta-regression
data(cholesterol)
m <- metaLik(heart_disease~chol_reduction, data=cholesterol, weights=1/sigma2)
summary(m)
|
Likelihood inference in random-effects meta-analysis models
Call:
metaLik(formula = y ~ 1, data = education, sigma2 = sigma2)
Estimated heterogeneity parameter tau2 = 0.03829
Fixed-effects:
estimate std.err. signed logLRT p-value Skovgaard p-value
(Intercept) 0.3004 0.0832 2.8989 0.0037 2.6778 0.0074
Log-likelihood: 8.3768
Likelihood inference in random-effects meta-analysis models
Call:
metaLik(formula = y ~ 1, data = albumin, sigma2 = sigma2)
Estimated heterogeneity parameter tau2 = 7.071e-05
Fixed-effects:
estimate std.err. signed logLRT p-value Skovgaard p-value
(Intercept) 60.9949 0.5457 27.9857 0 25.4928 0
Log-likelihood: -2.163
Likelihood inference in random-effects meta-analysis models
Call:
metaLik(formula = y ~ latitude, data = vaccine, sigma2 = sigma2)
Estimated heterogeneity parameter tau2 = 0.1676
Fixed-effects:
estimate std.err. signed logLRT p-value Skovgaard p-value
(Intercept) -0.3050 0.2241 -1.3378 0.181 -1.2245 0.2208
latitude -0.0154 0.0064 -2.1203 0.034 -1.8164 0.0693
Log-likelihood: 1.1212
Likelihood inference in random-effects meta-analysis models
Call:
metaLik(formula = heart_disease ~ chol_reduction, data = cholesterol,
weights = 1/sigma2)
Estimated heterogeneity parameter tau2 = 7.071e-05
Fixed-effects:
estimate std.err. signed logLRT p-value Skovgaard p-value
(Intercept) 0.1210 0.0974 1.2498 0.2114 1.3597 0.1739
chol_reduction -0.4757 0.1384 -3.0323 0.0024 -2.4606 0.0139
Log-likelihood: 15.1519
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