MoEClust: Gaussian Parsimonious Clustering Models

with Gating and Expert Network Covariates

and a Noise Component

MoEClust v1.6.0 - (18^th release [minor update]: 2025-03-05)

New Features & Improvements

• Various improvements to MoE_gpairs (also see additional Bug Fixes below):
  • Significant fixes when there are expert covariates and diag.pars$show.dens=TRUE &/or
    response.type="density" by properly using log average density instead of average log density.
  • Marginal densities when diag.pars$show.dens=TRUE are now always evaluated over evenly-spaced
    grids, the size of which can now be modified via diag.pars$diag.grid (equal to 100, by default):
    previously, the grids were formed using the observed values, which led to strange behaviour.
  • Added density.pars$dens.points=FALSE for overlaying points when response.type="density".
  • Various improvements in relation to subset args.:
    • data.ind & cov.ind can now be character strings / variable names (previously numeric indices only).
    • Added submat for showing only "upper"/"lower" triangular & "diagonal" plot panels.
    • When submat="all", the slowness of response.type="density" plots is now offset
      by using densities pre-calculated from upper-triangular panels for lower-triangular panels.
• MoE_Uncertainty gains two new arguments:
  • col: default of "cluster" colours according to cluster-membership, but
    old behaviour of highlighting uncertain observations can be recovered via col="uncertain".
  • rug1d (TRUE, by default) for use with univariate models, which puts
    the actual observed values along the x axis when type="barplot".
• MoE_control gains new init.z option "soft.random": the "random" option has been
  renamed to "random.hard", but init.z="random" will work as before due to partial matching.
• tau0 can now always be supplied as a vector (previously allowed only with gating covariates & noise.gate=TRUE).
• Speed improvements by replacing matrixStats::rowLogSumExps with new logsumexp & softmax
  functions from mclust (w/ mclust (>= 6.1) now ensured in Imports:) where appropriate throughout.
• stats::lm.wfit-related speed-ups from previous update now extend to MoE_gpairs with scatter.type="lm".
• Further related minor speed-ups for models with G == 0 and G == 1.

Bug Fixes & Miscellaneous Edits

• Additional minor fixes to MoE_gpairs:
  • Subsetting is now allowed to result in only one single panel.
  • Additional edits in relation to diag.pars$show.dens:
    • show.dens=TRUE now works properly when subset$data.ind is used.
    • The expert.covar arg. is no longer invoked when show.dens=TRUE.
    • Fixed (i.e. increased) height of diagonal panels when show.dens=TRUE &/or show.hist=TRUE.
  • Additional edits in relation to barcode panels:
    • Partially fixed dimensions of vertical panels when conditional="barcode"
      (caution still advised when using RStudio’s “Plots” pane if non-square).
    • Barcode panels now have colour throughout (previously only MAP-related panels),
      with related minor fixes when barcode.pars$use.points=TRUE.
  • Minor label-related adjustments:
    • Outer labels of mosaic panels are now correct when diagonal=FALSE.
    • Cosmetic adjustments to default orientation of labels matching categorical variable levels.
    • density.pars$show.labels="mixed" now works properly.
  • Many documentation improvements & clarifications.
• Minor fixes in relation to MoECriterion objects and MoE_plotCrit:
  • Bug fix in relation to non-finite values for direct plots of MoECriterion objects, e.g. plot(x$BIC).
  • crit="loglik" formerly erroneously produced the same plot as crit="aic".
  • New crit options "df" & "iters" added.
• Fixed bugs when a ‘soft’ z.list is supplied when algo != "EM".
• MoE_estep & MoE_cstep now work when there is only one observation, with a related
  fix to predict.MoEClust(..., use.y=TRUE) when predicting only one observation.
• Fixed extremely rare bug in MoE_clust & associated predict, fitted, & residuals methods
  when algo="CEM" and a model has only one observation/prediction assigned to its noise component.
• Fixed minor bug when as.Mclust is used with expert.covar=TRUE for multivariate models
  with expert network covariates and subsequently used to produce density-related plots.
• Additional minor documentation improvements.

MoEClust v1.5.2 - (17^th release [patch update]: 2023-12-10)

New Features, Improvements, Bug Fixes, & Miscellaneous Edits

• Massive speed-ups for models w/ expert covariates by replacing stats::lm w/ stats::lm.wfit:
  returned output in x$expert is still formatted as per stats::lm.
• Semi-related fixes to expert & gating network output for models w/ no covariates in those parts:
  coefficients now accurately reflect corresponding estimates of means & mixing proportions
  (especially for models with a noise component &/or equalPro=TRUE).
• MoE_entropy and MoE_AvePP both gain the arg. group for computing the average entropies
  and posterior probabilities of each component, respectively: defaults to FALSE, i.e. old behaviour.
• Added FARI for computing the Frobenius (adjusted) Rand index between two soft &/or hard partitions.
• Fixed bug in as.Mclust for models w/ gating & expert covariates when expert.covar=TRUE.
• Extensive edits to avoid overheads introduced in matrixStats (>= 1.0.0) + related minor speed-ups.
• Now using newer CITATION commands & updated License: GPL (>= 3).

MoEClust v1.5.1 - (16^th release [patch update]: 2022-12-19)

New Features, Improvements, Bug Fixes, & Miscellaneous Edits

• New MoE_gpairs arg. diag.pars$show.dens=FALSE added to toggle whether
  parametric density estimates are drawn over diagonal panels for each response
  variable (with or without the underlying histograms; see documentation).
• New function MoE_Similarity added and integrated into plot.MoEClust.
• New function MoE_AvePP added.
• Minor speed-ups to MoE_mahala for univariate data with (default) identity=FALSE.

MoEClust v1.5.0 - (15^th release [minor update]: 2022-03-28)

Significant User-Visible Changes

• Checks/fixes for empty components extended to components w/ <=1 observations (or equivalent):
  important — some rare cases which previously would not converge will now converge!
• Fixed significant bugs related to exp.init$malanabis=TRUE (the default) introduced in v1.4.1,
  important — restored correct behaviour, especially when multiple modelNames are being fitted!

New Features & Improvements

• New function MoE_entropy added.
• Added summary (and related print) methods for MoECriterion objects.
• Minor speed-up to E-step for "EEE" & "VVV" models.

Bug Fixes & Miscellaneous Edits

• Allowed G=0:X in MoE_clust without adding noise for G>0, unless
  specifying models w/ noise, undoing another bug introduced in v1.4.1.
• Fixed minor bug when supplying modelNames when G=1 only.
• Fixed check on validity of hc.meth arg. in MoE_control.
• Minor documentation clarifications re: z.list in MoE_control.

MoEClust v1.4.2 - (14^th release [patch update]: 2021-12-19)

New Features, Improvements, Bug Fixes, & Miscellaneous Edits

• MoE_mahala arg. identity (& related MoE_control exp.init$identity option) is now also
  relevant for univariate data: old behaviour is retained via respective defaults of FALSE & TRUE for
  multivariate & univariate data (i.e. only ability to set identity=FALSE for univariate data is new).
• Fixed MoE_clust bug when tau0 is specified but G is not (introduced in last update).
• Minor speed-up to MoE_gpairs(response.type="density") w/ expert covariates & noise component.
• MoE_gpairs arg. density.pars$grid.size now recycled as vector of length 2 if supplied as scalar.
• aitken now returns ldiff, the difference in log-likelihood estimates used for the stopping criterion.
• sapply replaced with vapply, with other negligible speed-ups.

MoEClust v1.4.1 - (13^th release [patch update]: 2021-10-12)

New Features, Improvements, Bug Fixes, & Miscellaneous Edits

• Various further fixes to MoE_stepwise:
  • Added the arg. fullMoE (defaulting to FALSE) which allows restricting the search to “full”
    MoE models where the same set of covariates appears in both the gating & expert networks.
  • When initialModel/initialG is given, the "all" option for noise.gate & equalPro
    now reverts to "both" whenever "all" would unnecessarily duplicate candidate models.
  • Small speed-up if gating &/or expert have covariates that are already in initialModel.
  • Small speed-up by searching G=1 equalPro models w/ expert covariates only once.
  • Two fixes to handle how initialModel and modelNames interact:
    • It’s now assumed (else warned) that initialModel should be optimal w.r.t. model type.
    • The supplied modelNames are augmented with initialModel$modelName if needs be.
• MoE_control gains the arg. exp.init$estart so the paper’s Algorithm 1 can work as intended:
  exp.init$estart toggles the behaviour of init.z="random" in the presence of expert covariates
  when exp.init$mahalanobis=TRUE & nstarts > 1: when FALSE (the default/old behaviour), all
  random starts are put through the initial reallocation routine and then subjected to full runs of the EM;
  when TRUE, only the single best random start obtained from this routine is subjected to the full EM.
• Handled name mismatches for optional args. w/ list(...) defaults in MoE_control/MoE_gpairs.
• Fixed printing of noise.gate in MoE_compare for G=1 models w/ noise & gating covariates.
• Improved checks on G in MoE_clust.

MoEClust v1.4.0 - (12^th release [minor update]: 2021-06-21)

New Features & Improvements

• Various edits to MoE_stepwise() (thanks, in part, to requests from Dr. Konstantinos Perrakis):
  • Added initialModel arg. for specifying an initial model from which to begin the search,
    which may already be a mixture and may already include covariates, etc.
  • Added initialG arg. as a simpler alternative when the only available
    prior information is on the number of components.
  • Added stepG arg. (defaults to TRUE) for fixing the number of components
    & searching only over different covariate configurations (i.e. when FALSE).
  • Speedups by preventing superfluous searches for equal
    mixing proportion models when there are gating covariates.
  • noise.gate arg. now also invoked when adding components to models with gating covariates
    & a noise component (previously only when adding gating covariates to models with noise).
  • equalPro & noise.gate args. gain new default "all" (see documentation for details).
  • Stronger checks on network.data argument.
• New methods and edits related to prediction:
  • Added fitted method for "MoEClust"objects (a wrapper to predict.MoEClust).
  • Added predict, fitted, & residuals methods for "MoE_gating" objects, i.e. x$gating.
  • Added predict, fitted, & residuals methods for "MoE_expert" objects, i.e. x$expert.
  • Minor edits to predict.MoEClust for models without expert network covariates.
  • Minor fixes to returned x$gating object for equalPro=TRUE models with a noise component.
• Various edits & documentation improvements to MoE_gpairs:
  • Fixes to ellipses for models with expert covariates due to fix to expert_covar (see below).
  • mosaic.pars gains logical arg. mfill=TRUE, to toggle between filling select tiles with colour
    (new default behaviour), or outlining select tiles with colour (old behaviour).
  • boxplot.pars arg. added to allow customising boxplot and violin plot panels,
    with related fixes to colourisation in upper-triangular panels.
  • Fixes re: scatter.pars$eci.col: now governs colours of ellipses and regression lines.
  • scatter.pars$uncert.pch added; now plotting symbols in covariate-related scatterplots
    are only modified in response.type="uncertainty" plots when uncert.cov is TRUE.
  • Fixes to axis labels for diagonal panels involving factors.
  • Various colour-related args. now inherit sensible defaults if scatterplot colours are specified.
• expert_covar gains the arg. weighted to ensure cluster membership probabilities are properly
  accounted for in estimating the extra variability due to the component means: defaults to TRUE,
  but weighted=FALSE is provided as an option for recovering the old (not recommended) behaviour.
• Minor speed-up to initialisation for univariate response data with expert network covariates.
• Minor speed-ups to some other utility functions.

Bug Fixes & Miscellaneous Edits

• A warning message is now printed if the MLR in the gating network ever fails to converge,
  prompting the user to modify the itmax arg. to MoE_control: the 3^rd element of this arg. governs
  the maximum number of MLR iterations — consequently, its default has been modified from 100 to
  1000 (thanks to a prompt from Dr. Georgios Karagiannis), which has the effect of slowing down
  internal calls to nnet::multinom but generally reduces the required number of EM iterations.
• Minor fix to MoE_compare whenever the optimal model needs to be refitted.
• Fixed conflict between mclust::as.Mclust & MoEClust::as.Mclust:
  as.Mclust.MoEClust now works regardless of order in which mclust & MoEClust are loaded.
• Stronger checks for variables in gating & expert formulas which are not found in network.data.
• Minor documentation, vignette, and vignette styling edits.

MoEClust v1.3.3 - (11^th release [patch update]: 2020-12-29)

New Features, Improvements, Bug Fixes, & Miscellaneous Edits

• Minor MoE_stepwise speed-ups by avoiding duplication of initialisation for certain steps.
• Minor fix to MoE_stepwise for univariate data sets without covariates.
• Prettier axis labels for MoE_uncertainty plots.
• Minor CRAN compliance edits to the vignette.

MoEClust v1.3.2 - (10^th release [patch update]: 2020-11-17)

New Features, Improvements, Bug Fixes, & Miscellaneous Edits

• New MoE_control arg. posidens=TRUE ensures code no longer crashes when observations
  have positive log-density: previous behaviour is recoverable by setting posidens=FALSE.
• MoE_control gains the arg. asMclust (FALSE, by default) which modifies the
  stopping and hcUse arguments such that MoEClust and mclust behave similarly
  for models with no covariates in either network (thanks to a request from Prof. Kamel Gana).
• Fixes to plotting colours & symbols in MoE_gpairs (thanks to Dr. Natasha De Manincor):
  • Corrected mosaic panels (colours).
  • Accounted for empty clusters in all panels (colours & symbols).
• Fixed bug in predict.MoEClust when no newdata is supplied to models with no gating covariates.
• MoE_clust & MoE_stepwise now coerce "character" covariates to "factor" (for later plotting).
• Further improvements to summary method for MoE_expert objects.
• Fixes to print & summary methods for MoE_gating objects if G=1 or equalPro=TRUE.
• Additional minor edits to MoE_plotGate.
• print.MoECompare gains the args. maxi, posidens=TRUE, & rerank=FALSE.
• Ensured lattice (>= 0.12), matrixStats (>= 0.53.1), & mclust (>= 5.4) in Imports:.
• Ensured clustMD (>= 1.2.1) and geometry (>= 0.4.0) in Suggests:.
• Use of NCOL/NROW where appropriate.
• Package startup message now checks if newer version of package is available from CRAN.
• Updated citation info after publication in Advances in Data Analysis and Classification.
• Updated maintainer e-mail address.
• Minor documentation, examples, and CRAN compliance + mclust compatibility edits.

MoEClust v1.3.1 - (9^th release [patch update]: 2020-05-12)

New Features, Improvements, Bug Fixes, & Miscellaneous Edits

• Maintenance release for compatibility with R 4.0.0 - minor edits.
• summary.MoEClust gains the printing-related arguments classification=TRUE,
  parameters=FALSE, and networks=FALSE (thanks to a request from Prof. Kamel Gana).
• Related improvements to print/summary methods for MoE_gating & MoE_expert objects.
• Minor speed-up for G=1 models with expert network covariates.
• Improvements to MoE_plotGate, with new type, pch, and xlab defaults.
• Added informative dimnames to returned parameters from MoE_clust().
• Documentation, vignette, examples, and references improvements.

MoEClust v1.3.0 - (8^th release [minor update]: 2020-03-30)

New Features & Improvements

• Various fixes and improvements to initialisation when there are expert network covariates:
  • MoE_mahala now correctly uses the covariance of resids rather than the response.
  • New MoE_mahala arg. identity allows use of Euclidean distance instead:
    this argument can also be passed via exp.init$identity to MoE_control.
  • Convergence of the initialisation procedure now explicitly monitored & sped-up.
  • Values of the criterion being minimised are now returned as an attribute.
  • The number of iterations of the initialisation algorithm are also returned as an attribute.
  • MoE_control arg. exp.init$max.init now defaults to .Machine$integer.max.
  • Improved checks on the resids arg. to MoE_mahala.
  • Greatly expanded the MoE_mahala examples.
• Improvements to predict.MoEClust:
  • Now returns the predicted values of the gating and expert networks.
  • Now returns the predictions from the expert network of the most probable component
    (MAPy), in addition to the (aggregated) predicted responses (y).
  • New arg. MAPresids governs whether residuals are computed against MAPy or y.
  • New arg. use.y (see documentation for details).
  • Now properly allows empty newdata for models with no covariates of any kind.
  • Fixed prediction for equal mixing proportion models when discard.noise=FALSE.
• Odds ratios now returned (and printed) when calling summary on x$gating.

Bug Fixes & Miscellaneous Edits

• Fixed small MoE_stepwise bugs when
  • only one of gating or expert are supplied.
  • univariate response data are supplied.
  • moving from G=1 to G=2 with equal mixing proportions and no covariates.
  • discarding covariates present in the response data.
• noise_vol now returns correct location for univariate data when reciprocal=TRUE.
• Spell-checking of documentation and fixes to donttest examples.

MoEClust v1.2.4 - (7^th release [patch update]: 2019-12-11)

New Features, Improvements, Bug Fixes, & Miscellaneous Edits

• Fixed small bugs in MoE_stepwise:
  • Improved checks on network.data and data.
  • Prevented z.list from being suppliable.
    
  • Fixes whenequalPro="yes" & noise=TRUE.
  • Fixes for supplying optional MoE_control arguments (also for MoE_clust).
  • Prevented termination if adding a component fails,
    provided at least one other step doesn’t fail.
• Fixed discard.noise=TRUE behaviour for MoE_clust, predict.MoEClust, &
  residuals.MoEClust for models with a noise component fitted via "CEM".
• Minor fixes to noise_vol function and handling of noise.meth arg. to MoE_control.
• Slight speed-up to E-step/C-step for models with a noise component.
• Initial allocation matrices now stored as attributes to MoE_clust output (see ?MoE_control).
• Anti-aliasing of vignette images.
• Updated citation info after online publication in Advances in Data Analysis and Classification.

MoEClust v1.2.3 - (6^th release [patch update]: 2019-07-29)

New Features, Improvements, Bug Fixes, & Miscellaneous Edits

• Exported function MoE_stepwise for conducting a greedy forward stepwise
  search to find the optimal model in terms of the number of components, GPCM
  covariance parameterisation, and the subsets of gating/expert network covariates.
• MoE_control & predict.MoEClust gain the arg. discard.noise:
  Default of FALSE retains old behaviour (see documentation for details).
• MoE_control gains the arg. z.list and the init.z arg. gets the option "list":
  this allows manually supplying (soft or hard) initial cluster allocation matrices.
• New args. and small fixes added to MoE_gpairs:
  • uncert.cov arg. added to control uncertainty point-size in panels with covariates.
  • density.pars gains arg. label.style.
  • scatter.pars & stripplot.pars gain args. noise.size & size.noise.
  • barcode.pars$bar.col slightly fixed from previous update.
  • Colours for "violin" type plots now accurate for MAP panels.
• Slight speed-up to noise_vol when method="ellipsoidhull".
• Small fix to predict.MoEClust when resid=TRUE for models with expert covariates.
• Small fix related to ... construct for residuals.MoEClust.
• All printing related to noise-only models no longer shows the model name (there is none!).
• Other small fixes to print.MoEClust, print.summary_MoEClust, & print.MoECompare.
• Cosmetic fix to returned gating objects for equalPro=TRUE models.
• Removed parallel package from Suggests:.

MoEClust v1.2.2 - (5^th release [patch update]: 2019-05-15)

New Features, Improvements, Bug Fixes, & Miscellaneous Edits

• noise_vol now also returns the location of the centre of mass of the region
  used to estimate the hypervolume, regardless of the method employed. This fixes:
  • predict.MoEClust for any models with a noise component (see below).
  • The summary of means for models with expert covariates and a noise component.
  • The location of the MVN ellipses for such models in MoE_gpairs (see below).
• Furthermore, calculation of the hypervolume in noise_vol for data with >2 dimensions
  is now correct when method="ellipsoidhull", owing to a bug in the cluster package.
• Other fixes and speed-ups for the MoE_gpairs plotting function:
  • Added arg. expert.covar (& also to as.Mclust function).
  • Fixed location of MVN ellipses for models with noise & expert covariates (see above).
  • Fixes when response.type="density" for all models with a noise component.
  • Speed-up when response.type="density" for models with covariates of any kind.
  • Fixes to labelling for models with a noise component.
  • Fixed handling of subset$data.ind & subset$cov.ind arguments.
  • Barcode type plots now have colour for panels involving the MAP classification.
  • Barcode type plots now respect the arg. buffer.
  • Use of colour in MoE_plotGate is now consistent with MoE_gpairs.
• Fixes to how gating & expert formulas are handled:
  • Allowed specification of formulas with dropped variables of the form ~.-a-b.
  • Allowed formulas with no intercept of the form ~c-1.
  • Allowed interaction effects, transformations and higher-order terms using I().
  • Small related fixes to drop_levels & drop_constants functions.
    
• MoE_compare gains arg. noise.vol for overriding the noise.meth arg.:
  this allows specifying an improper uniform density directly via the (hyper)volume,
  & hence adding noise to models for high-dimensional data for which noise_vol() fails.
• Fixed bug for equalPro models with noise component, and also added equalNoise arg.
  to MoE_control, further controlling equalPro in the presence of a noise component.
• Fixes to predict.MoEClust for the following special cases:
  • Fixes for any models with a noise component (see noise_vol comment above).
  • Accounted for predictions of single observations for models with a noise component.
  • Accounted for models with equal mixing proportions.
• Accounted for categorical covariates in the x.axis arg. to MoE_plotGate.
• tau0 can now also be supplied as a vector when gating covariates are used & noise.gate=TRUE.
• Fix to expert_covar for univariate models.
• Slight MoE_estep speed-up due to removal of unnecessary sweep().
• Small fixes for when clustMD is invoked, and added snow package to Suggests:.
• The nnet arg. MaxNWts now passable to gating network multinom call via MoE_control.
• Improved printing of output and handling of ties, especially for MoE_compare.
• Many documentation and vignette improvements.

MoEClust v1.2.1 - (4^th release [patch update]: 2018-12-11)

New Features, Improvements, Bug Fixes, & Miscellaneous Edits

• New MoE_control arg. algo allows model fitting using the "EM" or "CEM" algorithm:
  • Related new function MoE_cstep added.
  • Extra algo option "cemEM" allows running EM starting from convergence of CEM.
• Added LOGLIK to MoE_clust output, giving maximal log-likelihood values for all fitted models.
  • Behaves exactly as per DF/ITERS, etc., with associated printing/plotting functions.
  • Edited MoE_compare, summary.MoEClust, & MoE_plotCrit accordingly.
• New MoE_control arg. nstarts allows for multiple random starts when init.z="random".
• New MoE_control arg. tau0 provides another means of initialising the noise component.
• If clustMD is invoked for initialisation, models are now run more quickly in parallel.
• MoE_plotGate now allows a user-specified x-axis against which mixing proportions are plotted.
• Fixed bug in checking for strictly increasing log-likelihood estimates.

MoEClust v1.2.0 - (3^rd release [minor update]: 2018-08-24)

New Features & Improvements

• New predict.MoEClust function added: predicts cluster membership probability,
  MAP classification, and fitted response, using only new covariates or new covariates &
  new response data, with noise components (and the noise.gate option) accounted for.
• New plotting function MoE_Uncertainty added (callable within plot.MoEClust):
  visualises clustering uncertainty in the form of a barplot or an ordered profile plot,
  allowing reference to be made to the true labels, or not, in both cases.
• Specifying response.type="density" to MoE_gpairs now works properly for models with
  gating &/or expert network covariates. Previous approach which evaluated the density using
  averaged gates &/or averaged means replaced by more computationally expensive but correct
  approach, which evaluates MVN density for every observation individually and then averages.
• Added clustMD package to Suggests:. New MoE_control argument exp.init$clustMD
  governs whether categorical/ordinal covariates are also incorporated into the initialisation
  when isTRUE(exp.init$joint) & clustMD is loaded (defaults to FALSE, works with noise).
• Added drop.break arg. to MoE_control for further control over the extra initialisation
  step invoked in the presence of expert covariates (see Documentation for details).
• Sped-up MoE_dens for the EEE & VVV models by using already available Cholesky factors.
• Other new MoE_control arguments:
  • km.args specifies kstarts & kiters when init.z="kmeans".
  • Consolidated args. related to init.z="hc" & noise into hc.args & noise.args.
  • hc.args now also passed to call to mclust when init.z="mclust".
  • init.crit ("bic"/"icl") controls selection of optimal mclust/clustMD
    model type to initialise with (if init.z="mclust" or isTRUE(exp.init$clustMD));
    relatedly, initialisation now sped-up when init.z="mclust".

Bug Fixes & Miscellaneous Edits

• ITERS replaces iters as the matrix of the number of EM iterations in MoE_clust output:
  • iters now gives this number for the optimal model.
    • ITERS now behaves like BIC/ICL etc. in inheriting the "MoECriterion" class.
      
    • iters now filters down to summary.MoEClust and the associated printing function.
      
    • ITERS now filters down to MoE_compare and the associated printing function.
• Fixed point-size, transparency, & plotting symbols when response.type="uncertainty"
  within MoE_gpairs to better conform to mclust: previously no transparency.
• subset arg. to MoE_gpairs now allows data.ind=0 or cov.ind=0, allowing plotting of
  response variables or plotting of the covariates to be suppressed entirely.
• Clarified MVN ellipses in MoE_gpairs plots.
• sigs arg. to MoE_dens & MoE_estep must now be a variance object, as per variance
  in the parameters list from MoE_clust & mclust output, the number of clusters G,
  variables d & modelName is inferred from this object: the arg. modelName was removed.
• MoE_clust no longer returns an error if init.z="mclust" when no gating/expert network
  covariates are supplied; instead, init.z="hc" is used to better reproduce mclust output.
• resid.data now returned by MoE_clust as a list, to better conform to MoE_dens.
• Renamed functions MoE_aitken & MoE_qclass to aitken & quant_clust, respectively.
• Rows of data w/ missing values now dropped for gating/expert covariates too (MoE_clust).
• Logical covariates in gating/expert networks now coerced to factors.
• Fixed small bug calculating linf within aitken & the associated stopping criterion.
• Final linf estimate now returned for optimal model when stopping="aitken" & G > 1.
• Removed redundant extra M-step after convergence for models without expert covariates.
• Removed redundant & erroneous resid & residuals args. to as.Mclust & MoE_gpairs.
• MoE_plotCrit, MoE_plotGate & MoE_plotLogLik now invisibly return relevant quantities.
• Corrected degrees of freedom calculation for G=0 models when noise.init is not supplied.
• Fixed drop_levels to handle alphanumeric variable names and ordinal variables.
• Fixed MoE_compare when a mix of models with and without a noise component are supplied.
• Fixed MoE_compare when optimal model has to be re-fit due to mismatched criterion.
• Fixed y-axis labelling of MoE_Uncertainty plots.
• print.MoECompare now has a digits arg. to control rounding of printed output.
• Better handling of tied model-selection criteria values in MoE_clust & MoE_compare.
• Interactions and higher-order terms are now accounted for within drop_constants.
• Replaced certain instances of is.list(x) with inherits(x, "list") for stricter checking.
• Added extra checks for invalid gating &/or expert covariates within MoE_clust.
• Added mclust::clustCombi/clustCombiOptim examples to as.Mclust documentation.
• Added extra precautions for empty clusters: during initialisation & during EM.
• Added utility function MoE_news for accessing this NEWS file.
• Added message if optimum G is at either end of the range considered.
• Tidied indentation/line-breaks for cat/message/warning calls for printing clarity.
• Added line-breaks to usage sections of multi-argument functions.
• Corrected MoEClust-package help file (formerly just MoEClust).
• Many documentation clarifications.

MoEClust v1.1.0 - (2^nd release [minor update]: 2018-02-06)

New Features & Improvements

• MoE_control gains the noise.gate argument (defaults to TRUE): when FALSE,
  the noise component’s mixing proportion isn’t influenced by gating network covariates.
• x$parameters$mean is now reported as the posterior mean of the fitted values when
  there are expert network covariates: when there are no expert covariates, the posterior
  mean of the response is reported, as before. This effects the centres of the MVN ellipses
  in response vs. response panels of MoE_gpairs plots when there are expert covariates.
• New function expert_covar used to account for variability in the means, in the presence
  of expert covariates, in order to modify shape & size of MVN ellipses in visualisations.
• MoE_control gains the hcUse argument (defaults to "VARS" as per old mclust versions).
• MoE_mahala gains the squared argument + speedup/matrix-inversion improvements.
• Speed-ups, incl. functions from matrixStats (on which MoEClust already depended).
• The MoE_gpairs argument addEllipses gains the option "both".

Bug Fixes & Miscellaneous Edits

• Fixed bug when equalPro=TRUE in the presence of a noise component when there are
  no gating covariates: now only the mixing proportions of the non-noise components
  are constrained to be equal, after accounting for the noise component.
• MoE_gpairs argument scatter.type gains the options lm2 & ci2 for further control
  over gating covariates. Fixed related bug whereby lm & ci type plots were being
  erroneously produced for panels involving pairs of continuous covariates only.
• Fixed bugs in MoE_mahala and in expert network estimation with a noise component.
• G=0 models w/ noise component only can now be fitted without having to supply noise.init.
• MoE_compare now correctly prints noise information for sub-optimal models.
• Slight edit to criterion used when stopping="relative": now conforms to mclust.
• Added check.margin=FALSE to calls to sweep().
• Added call.=FALSE to all stop() messages.
• Removed dependency on the grid library.
• Many documentation clarifications.

MoEClust v1.0.0 - (1^st release: 2017-11-28)