fpc (version 2.2-9)

# 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`.

## References

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

## Examples

```# NOT RUN {
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
# }
```