Convenience functions for analyzing factorial experiments using ANOVA or mixed models. aov_ez(), aov_car(), and aov_4() allow specification of between, within (i.e., repeated-measures), or mixed between-within (i.e., split-plot) ANOVAs for data in long format (i.e., one observation per row), aggregating multiple observations per individual and cell of the design. mixed() fits mixed models using lme4::lmer() and computes p-values for all fixed effects using either Kenward-Roger or Satterthwaite approximation for degrees of freedom (LMM only), parametric bootstrap (LMMs and GLMMs), or likelihood ratio tests (LMMs and GLMMs). afex uses type 3 sums of squares as default (imitating commercial statistical software).

```
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** afex VERSION 0.15-x **
*************************
Changes in afex Version 0.15-x
Released October 2015
Significant User Visible Changes and New Features
o added p.adjust.method argument for ANOVA functions (anova and nice
methods). Can be used to control for multiple comparisons in
exploratory ANOVAs (see Cramer, et al., 2015; PB&R). Functionality
contributed by Frederik Aust (https://github.com/singmann/afex/pull/3).
Bugfixes
o ANOVA functions work with dplyr data.frames now (data is transformed
via as.data.frame). See: https://github.com/singmann/afex/issues/6
o formulas for mixed can now be of a maximum length of 500 characters
(was 60 chars previously): https://github.com/singmann/afex/issues/5
o aov_car et al. did not work with within-subject factors that were also
included outside the Error term. This was caused by the use of regular
expressions not appropriate for the new stringi backend of stringr.
Thanks to Tom Wenseleers for reporting this bug.
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** afex VERSION 0.14-x **
*************************
Changes in afex Version 0.14-x
Released August 2015
Significant User Visible Changes and New Features
o new default return argument for ANOVA functions, afex_aov,
an S3 object containing the following:
(1) ANOVA table of class "anova"
(2) ANOVA fitted with base R's aov (can be passed to lsmeans
for post-hoc tests)
(3) output from car::Anova (for tests of effects),
ANOVA table (1) is based on this model
(4) lm object passed to car::Anova
(5) data used for estimating (2) and (4)
o added support for lsmeans: objects of class afex_aov can be
passed to lsmeans directly. afex now depends on lsmeans.
o added afex_options() functionality for setting options globally.
o added expand_re argument to mixed which, if TRUE, correctly interprets
the || notation in random effects with factors (i.e., suppresses
estimation of correlation among random effects). lmer_alt is a wrapper
for mixed which uses expand_re = TRUE, returns an object of class
merMod (i.e., does not calculate p-values), and otherwise behaves
like g/lmer (i.e., does not enforce certain contrasts)
o added three new data sets (Singmann & Klauer, 2011; Klauer &
Singmann, 2013) and a vignette showing how to calculate
contrasts after ANOVA.
o ANOVA functions renamed to aov_car, aov_ez, and aov_4. Old
functions are now deprecated.
o first element in mixed object renamed to anova_table.
o nice.anova renamed to nice. nice() can be called for afex_aov
and mixed objects and returns a nicely formatted (numbers
converted to characters) results table (which is also the
default print method for both objects).
o anova() can be called for afex_aov and mixed objects and returns
the numeric anova table (i.e., the first element of each object).
There also exists print methods for those data.frames.
o summary method for mixed objects now calls summary.merMod on
full model.
o afex does not depend on car package anymore, it is only imported.
o afex is now hosted on github: https://github.com/singmann/afex
Bugfixes
o ANOVA: for "aov"-objects, contrasts are only set for factors.
o compare.2.vector failed when the two means were exactly equal
(due to an issue with median_test). This only throws a warning
now.
o compare.2.vector documentation updated for coin 1-1.0.
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** afex VERSION 0.13-x **
*************************
Changes in afex Version 0.13-x
Released January 2015
Significant User Visible Changes and New Features
o added ems() function for deriving the expected values of the
mean squares for factorial designs (contributed by Jake
Westfall).
Bugfixes
o aov.car et al. stop with error message if a factor has only one
level.
o aov.car transforms id variable to factor which ensures that
return = "aov" provides equivalent results.
o changed regex for detecting "observed" variables to work with
the new version of stringr which uses stringi.
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** afex VERSION 0.12-x **
*************************
Changes in afex Version 0.12-x
Released November 2014
Significant User Visible Changes and New Features
o ANOVA functions give informative error if some parameters are
not estimable (most likely due to structural missings, i.e.
empty cells).
Bugfixes
o mixed(..., method = "PB") does not fail anymore when only
having a single fixed effect (thanks to Kiyoshi Sasaki for
reporting it).
o aov.car() failed when a within-subject factor had empty levels.
Unused factor levels are now dropped. This bug was probably
introduced in Rev 126 as part of an attempt to solve a bug.
(thanks to Will Bowditch for reporting it).
*************************
** afex VERSION 0.11-x **
*************************
Changes in afex Version 0.11-x
Released October 2014
Significant User Visible Changes and New Features
o added allFit() function (written by Ben Bolker).
o mixed() gives warning if nested model provides worse fit
(logLik) than full model (when fitted with ML).
o print, summary, and anova method for mixed objects are now
identical.
o description of returned object from mixed() extended (Thanks
to Ben Bolker, see http://stackoverflow.com/a/25612960/289572)
o added return = "aov" to aov.car which returns the ANOVA
fitted with aov (with correct Error strata) so that it can be
passed to lsmeans for post-hoc tests or plotting (lsmip).
Bugfixes
o all required functions are now correctly imported avoiding
CRAN warnings and better functioning.
o data argument to lmer calls in mixed set correctly. Note that
still contrasts added to the data in mixed may prohibit use of
predict.merMod() or similar functions. It is recommended to
set the contrasts globally to "contr.sum", e.g.,
via set_sum_contrasts(), for correct functioning
(disable via set.data.arg argument for mixed).
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** afex VERSION 0.10-x **
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Changes in afex Version 0.10-x
Released August 2014
Significant User Visible Changes and New Features
o afex does not change the global contrasts anymore when loading
the package (due to popular demand).
o new functions to globally set contrasts: set_sum_contrasts &
set_treatment_contrasts (and some more wrappers).
o Added more mixed model examples from Maxwell & Delaney, Chapter
15 ("Multilevel Models for within subjects designs"), see ?mixed
and ?md_15.1. Thanks to Ulf Mertens.
Bugfixes
o removed bug when factor levels of within-subject factors
contained "+" or "-" and were not converted correctly. Added
tests for known bugs in aov.car.
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** afex VERSION 0.9-x **
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Changes in afex Version 0.9-x
Released April 2014
Significant User Visible Changes and New Features
o added function aov4: another wrapper of car::Anova for ANOVA
models specified via lme4::lmer syntax.
o added return="marginal" to aov.car which returns the marginal
means of all effects (i.e., grand mean and mean of main
effects and interactions). Is also returned if return="full".
o testing the intercept in mixed models in now only optional.
The default is that the new argument test.intercept = FALSE.
o removed return="lme4" from aov.car.
o added argument intercept to nice.anova (default FALSE) which
allows to selective display the intercept in an ANOVA table.
o added method = "F" to mixed() which only returns the F-value
but no ddf (and hence no p-value). Experimental, not documented.
o renamed colname "stat" to "F" when method = "KR" (mixed).
o added tests (currently mainly for mixed()) via pkg testthat,
see tests/testthat.
Bugfixes
o increased requirement of R version and lme4 version.
o print.mixed should now propagate all warnings from lme4 (i.e.,
also the new convergence warnings).
o lme4 is now loaded at worker nodes for mixed (default,
turn of via check.contrasts)
************************
** afex VERSION 0.8-x **
************************
Changes in afex Version 0.8-x
Released February 2014
Significant User Visible Changes and New Features
o removed renaming of within subject factor levels to names
with length 1 (which was introduced in 0.6).
o helper function round_ps which nicely rounds p-values
is now exported.
o warning about numerical non-centered variables in mixed
is now a message only.
o added examples data sets from Maxwell & Delaney (2004) for
within-subjects ANOVA and mixed models.
o reshape2 is now again in depends but coin only imported.
Bugfixes
o the default effect size (ges: generalized eta-squared) was
calculated wrong (the error term for the intercept was not
included). Sorry. This is now corrected (with new examples).
o removed bug that aov.car didn't work when running some ANCOVAs
(thanks to Gang Chen for reporting this).
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** afex VERSION 0.7-x **
************************
Changes in afex Version 0.7-x
Released December 2013
Significant User Visible Changes and New Features
o nicer output of print.mixed
Bugfixes
o mixed() correctly converts all non-formula arguments to
formula correctly to a formula (gave error if formula
was a different object and not-available on cluster nodes).
Prints message if formula is converted to a formula.
o Using multicore for fitting the models prodcued erroneous
results (did not use correct contrasts at nodes). Now the
current contrasts are also set at the nodes.
o mixed() sets REML = FALSE if method = "LRT" and no
family argument is present (i.e., for LMMs) as LRTs
for models fitted with REML are not recommended.
o on the cluster nodes now only the lme4 namespace is
loaded (instead of using library) to avoid a CRAN note.
************************
** afex VERSION 0.6-x **
************************
Changes in afex Version 0.6-x
Released September 2013
Significant User Visible Changes and New Features
o added LRT tests to mixed() which should replicate
the recommended test by Barr et al. (2013, JML).
o multicore estimation of (g)lmer models now available
through package parallel (argument cl) for mixed().
o added experimental "lme4" return method for
aov.car and ez.glm (which fits the data using lmer).
o reshape2 and stringr are not any more loaded when
loading afex (are now only imported via Imports)
Bugfixes
o Type 2 tests of mixed() were implemented incorrectly (i.e.,
they did not give what they should have given according
to the description in the help file).
o aov.car() and ez.glm() now convert factor levels of within
subjects factors to be of length one so that long levels
do not lead to problems when constructing the call to lm.
Thanks to Isaac Schwabacher for noticing this, see also:
https://bugs.r-project.org/bugzilla3/show_bug.cgi?id=15377
o mixed should now work with missing values as it construes
a new data object if the model.matrix from which the
different versions are fitted has nrow different to
nrow(data) (with warning). Thanks to Daniel Bunker
for reporting this.
o mixed should work with the newest version of lme4 (>= 1.0.4)
and the newst version of pbkrtest (>= 0.3-5.1), but not
with older versions (due to CRAN policy to disallow :::).
************************
** afex VERSION 0.5-x **
************************
Changes in afex Version 0.5-x
Released May 2013
Significant User Visible Changes and New Features
o added argument factorize (default: TRUE) to aov.car and ez.glm:
all variables are now factorized per default. (now it is
necessary to set factorize=FALSE for ANCOVAs!)
o added argument per.parameter to mixed() which allows to specify
variables for which each parameter is tested (not only the
overall effect). Can be useful to test for ordered factors.
(only implemented for "Type 3" tests)
o added more informative startup message (thanks to Robert Volcic
and Lars Konieczny)
o mixed, ez.glm and aov.car now check for correct contrasts and set
factors to contr.sum if other contrasts are found (can be tunred
off via check.contrasts argument). Resetting the default contrast
to contr.treatment should therefore not interfere with afex.
(this is not intensly tested, so please report anything)
o mixed checks numeric variables if they are centered on 0 (and
gives warning if not).
Bugfixes
o checks if observed variable is in the data and throws
an error if not (nice.anova)
************************
** afex VERSION 0.4-x **
************************
Changes in afex Version 0.4-x
Released February 2013
Significant User Visible Changes and New Features
o added generalized and partial eta-squared effect
sizes to nice.anova (this also included adding
observed arguments to aov.car, ez.glm, nice.anova)
o added new return arguments to aov.car and ez.glm
(nice, lm, data).
o changed default return value of aov.car and ez.glm
to "nice" which now returns a nice ANOVA table
(nice.anova)
o mixed has method = "PB" for obtaining parametric
bootstrapped p-values (e.g., for GLMMs)
o added alternative argument to compare.2.vectors.
o aov.car (and ez.glm) now give a warning if
observations are missing on within-subject factors.
(As before, cases with missing values are simply
excluded from the analysis)
o had to disable saving of the previous contrasts and
resetting those after detaching afex due to
CRAN policies (no assignment in global environment).
Bugfixes
o Bug when running mixed() inside a function and
handing the data.frame over as an argument fixed
(thanks, again, to Florent Duyme). See
bugs/eval.scoping.bug.R
o nice.anova did not work with a model with only one
within-subjects factor.
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** afex VERSION 0.3-x **
************************
Changes in afex Version 0.3-x
Released August/September 2012
Significant User Visible Changes and New Features
o added function compare.2.vectors().
o Name of function univariate() changed to univ(), as
a function with this name is part of package multcomp.
This may leed to problems. Thanks to Florent Duyme for
spotting this.
o added return argument to aov.car() and ez.glm().
o added rather dubious Type 2 tests to mixed().
o aov.car checks if each id is only present in one
cell of the between subjects design.
Bugfixes
o aov.car now uses do.call when calling lm() to avoid local
variables in the call to lm() which could led to problems when
working with the lm model.
o mixed() now passes ... (further arguments to lmer) correctly.
(Now mixed uses match.call and eval on the call instead of
invoking lmer directly.)
o corrected bug that was introduced by pbkrtest v3.2 when
invoking the print method to an object of class mixed
(again thanks to Florent Duyme for spotting this).
o removed bug when factor levels of within-subject factors
were non-legal names (solution uses make.names).
```