fpc: mergeparameters – R documentation

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mergeparameters

New parameters from merging two Gaussian mixture components

Description

Re-computes pointwise posterior probabilities, mean and covariance matrix for a mixture component obtained by merging two mixture components in a Gaussian mixture.

Usage

mergeparameters(xdata, j1, j2, probs, muarray,Sigmaarray, z)

Arguments

`xdata`	data (something that can be coerced into a matrix).
`j1`	integer. Number of first mixture component to be merged.
`j2`	integer. Number of second mixture component to be merged.
`probs`	vector of component proportions (for all components; should sum up to one).
`muarray`	matrix of component means (rows).
`Sigmaarray`	array of component covariance matrices (third dimension refers to component number).
`z`	matrix of observation- (row-)wise posterior probabilities of belonging to the components (columns).

Value

List with components

`probs`	see above; sum of probabilities for original components `j1` and `j2` is now `probs[j1]`. Note that generally, also for the further components, values for the merged component are in place `j1` and values in place `j2` are not changed. This means that in order to have only the information for the new mixture after merging, the entries in places `j2` need to be suppressed.
`muarray`	see above; weighted mean of means of component `j1` and `j2` is now in place `j1`.
`Sigmaarray`	see above; weighted covariance matrix handled as above.
`z`	see above; original entries for columns `j1` and `j2` are summed up and now in column `j1`.

Author(s)

Christian Hennig christian.hennig@unibo.it https://www.unibo.it/sitoweb/christian.hennig/en/

References

Hennig, C. (2010) Methods for merging Gaussian mixture components, Advances in Data Analysis and Classification, 4, 3-34.

Examples

options(digits=3)
  set.seed(98765)
  require(mclust)
  iriss <- iris[sample(150,20),-5]
  irisBIC <- mclustBIC(iriss)
  siris <- summary(irisBIC,iriss)
  probs <- siris$parameters$pro
  muarray <- siris$parameters$mean
  Sigmaarray <- siris$parameters$variance$sigma
  z <- siris$z
  mpi <- mergeparameters(iriss,1,2,probs,muarray,Sigmaarray,z)
  mpi$probs
  mpi$muarray

fpc

Flexible Procedures for Clustering

v2.2-9

GPL

Authors

Christian Hennig <christian.hennig@unibo.it>

Initial release

2020-12-06