summary.mixmeta function

Summarizing mixmeta Models

Print and summary method functions for fitted meta-analytical models represented in objects of class "mixmeta".

## S3 method for class 'mixmeta'
summary(object, ci.level=0.95, ...)

## S3 method for class 'summary.mixmeta'
print(x, digits=4, report=c("sd","var"), ...)

## S3 method for class 'mixmeta'
print(x, digits=4, ...)

Arguments

• object: an object of class "mixmeta" produced by a call to mixmeta.
• x: an object of class "mixmeta" or "summary.mixmeta", produced by calls to mixmeta or summary.mixmeta, respectively.
• ci.level: a numerical value between 0 and 1, specifying the confidence level for the computation of confidence intervals.
• digits: an integer specifying the number of digits to which printed results must be rounded.
• report: if standard deviations (sd) or variances (var) must be reported for summarizing the random-effects (co)variance structure.
• ...: further arguments passed to or from other methods.

Details

The print method function for class "mixmeta" only returns basic information on the fitted model, namely the call, estimated fixed-effects coefficients, dimensions and fit statistics (log-likelihood, AIC, BIC).

The summary method function computes additional statistics and tests, and produces a list object of class "summary.mixmeta". The print method function for this class shows additional information, such as tables reporting the estimates for the fixed and random-effects parts of the model, Cochran Q test for heterogeneity and I-squared.

Returns

The summary method function for mixmeta objects produces a list of class "summary.mixmeta". The components of the lists are some of those stored in the related mixmeta object, plus the following:

• coefficients: a matrix reporting point estimates, standard errors, z statistics and related p-values of the test, and confidence intervals for the $kp$ fixed-effects coefficients. Note this is different than the component with the same name stored in mixmeta objects, simply reporting the point estimates (see mixmetaObject).

• AIC: the value of the Akaike information criterion for the fitted mixmeta model, obtained through a call to AIC.

• BIC: the value of the Bayesian information criterion for the fitted mixmeta model, obtained through a call to BIC.

• corFixed: the $kp x kp$ correlation matrix of the fixed-effects coefficients, obtained from the (co)variance matrix vcov (see mixmetaObject and vcov).

• corRandom: the $kq x kq$ correlation matrix of the random effects, obtained from the random-effects (co)variance matrix Psi, or a list of multiple matrices for multilevel models. See mixmetaObject.

• qstat: results from the Cochran Q test for heterogeneity, namely a list corresponding to a qtest.mixmeta object without its class, obtained through qtest.

• i2stat: I-squared statistic for the meta-analytical model.

• ci.level: the confidence level used for defining the confidence intervals for the estimates of the fixed-effects coefficients.

As usual, the print method functions for classes "mixmeta" and "summary.mixmeta" do not return any value.

References

Sera F, Armstrong B, Blangiardo M, Gasparrini A (2019). An extended mixed-effects framework for meta-analysis.Statistics in Medicine. 2019;38(29):5429-5444. [Freely available list("here")].

Author(s)

Antonio Gasparrini <antonio.gasparrini@lshtm.ac.uk > and Francesco Sera <francesco.sera@lshtm.ac.uk >

See Also

See mixmeta and mixmetaObject.

Examples

# RUN THE MODEL
model <- mixmeta(cbind(PD,AL) ~ pubyear, S=berkey98[5:7], data=berkey98)

# SIMPLE PRINT
model

# DEFINE DIGITS
print(model, digit=2)

# SUMMARY WITH 80TH CONFIDENCE INTERVALS
summary(model, ci.level=0.80)

# REPORT RANDOM EFFECTS IN TERMS OF VARIANCES (USE print)
print(summary(model), report="var")