Dear Conductors,

I was wondering if there's any simple way of calculating the probability of
a point membership to a certain cluster. I'm using EM algorithm from mclust
package to analyse my data. As an output of classification I obtain data
grouped into clusters and I can have a matrix whose the element in position
[I,k] presents the conditional probability of the ith point belongs to the
kth cluster. However, I would like to get something more precise, as a
probability of belongness for each point only from given cluster. For
example, If I get my data divided into 3 groups by EM algorithm, I would
like to know how strong each point from cluster 1 belongs to this cluster, how
strong each point from cluster 2 belongs to this cluster and how strong
each point from cluster 3 belongs to this cluster. I was thinking about the
creating some kind of parameter, which will allow me to see points with
highest/strongest membership...like show me all points, which belong to
their clusters with probability higher than 0.8.

R Code:

library(mclust)

dataset1MC<-Mclust(dataset1)
plot(dataset1MC, dataset1)

dataset1MC$z

               [,1]         [,2]
NA12043 1.000000e+00 2.608455e-15
NA12249 1.000000e+00 7.784309e-15
NA12264 1.000000e+00 1.664289e-25
NA12707 1.000000e+00 2.869001e-18
NA12234 3.151495e-19 1.000000e+00
NA12236 1.000000e+00 4.399892e-21
NA12763 1.000000e+00 2.203443e-19
NA12801 1.000000e+00 7.568722e-21

sessionInfo()

R version 2.13.1 (2011-07-08)
Platform: x86_64-pc-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=Polish_Poland.1250  LC_CTYPE=Polish_Poland.1250
 LC_MONETARY=Polish_Poland.1250 LC_NUMERIC=C
LC_TIME=Polish_Poland.1250

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] mclust_3.4.10


I would be grateful for any help and clues

Best,
B.

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