Package Overview

Implements the Expectation Maximisation Algorithm for clustering the multivariate and univariate datasets. There are two versions of EM implemented-EM* (converge faster by avoiding revisiting the data) and EM. For more details on EM*, see the 'References' section below.

The package has been tested with both real and simulated datasets. The package comes bundled with a dataset for demonstration (ionosphere_data.csv). More help about the package can be seen by typing ?DCEM in the R console (after installing the package).

Currently, data imputation is not supported and user has to handle the missing data before using the package.

Contact

For any Bug Fixes/Feature Update(s)

[Parichit Sharma: parishar@iu.edu]

For Reporting Issues

Issues

Package Link on CRAN

DCEM on CRAN

Installation Instructions

Dependencies First, install all the required packages as follows:

install.packages(c("matrixcalc", "mvtnorm", "MASS", "Rcpp"))

Installing from CRAN

install.packages("DCEM"")

Installing from the Source Package

R CMD install DCEM_2.0.3.tar.gz

How to use the Package (Example: Working with the default bundled dataset)

• For demonstration purpose, users can call the dcem_test() function from the R console. This function invokes the dcem_star_train() on the bundled ionosphere_data. Alternatively, a minimal quick start example is given below that explain how to cluster the ionosphere_data from scratch.

# Example: Using the dcem_test()

# Load the library
library("DCEM")

# call the dcem_test() function and store the result in a variable
sample_out = dcem_test()

# Probe the returned values 
# Note: Detailed description of the returned values is also given in the section
# **_Displaying the output:_**

sample_out$prob         # estimated posterior probabilities
sample_out$meu          # estimated mean of the clusters
sample_out$sigma        # estimated covariance matrices
sample_out$priors       # estimated priors
sample_out$memebership  # membership of data points based on maximum liklihood (posterior probabilities)

An example of clustering the ionosphere data

• The DCEM package comes bundled with the ionosphere_data.csv for demonstration. Help about the dataset can be seen by typing ?ionosphere_data in the R console. Additional details can be seen at the link Ionosphere data.

• To use this dataset, paste the following code into the R console.

ionosphere_data = read.csv2(
  file = paste(trimws(getwd()),"/data/","ionosphere_data.csv",sep = ""),
  sep = ",",
  header = FALSE,
  stringsAsFactors = FALSE
)

• Cleaning the data: Before the model can be trained (dcem_train() function), the data must be cleaned. This simply means to remove all redundant columns (example can be label column). This dataset contains labels in the last column (35th) and only 0's in the 2nd column so let's remove them,

Paste the below code in the R session to clean the dataset.

ionosphere_data =  trim_data("35,2", ionosphere_data)

• Clustering the data: The dcem_train() learns the parameters of the Gaussian(s) from the input data.

Paste the below code in the R session to call the dcem_train() function.

dcem_out = dcem_train(data = ionosphere_data, threshold = 0.0001, iteration_count = 50, num_clusters = 2)

• Displaying the output: The list returned by the dcem_train() is stored in the dcem_out object. It contains the parameters associated with the clusters (Gaussian(s)). These parameters are namely - posterior probabilities, meu, sigma and priors. Paste the following code in the R session to access any/all the output parameters.

          [1] Posterior Probabilities: dcem_out$prob: A matrix of posterior-probabilities for the 
              points in the dataset.
              
          [2] Meu(s): dcem_out$meu
              
              For multivariate data: It is a matrix of meu(s). Each row in the  
              matrix corresponds to one meu.
              
              For univariate data: It is a vector if meu(s). Each element of the vector corresponds 
              to one meu.
              
          [3] Co-variance matrices 
          
              For multivariate data: dcem_out$sigma: List of co-variance matrices.
          
              For univariate data: dcem_out$sigma: Vector of standard deviation(s).
               
          [4] Priors: dcem_out$prior: A vector of prior.
          
          [5] Membership: dcem_out$membership: A vector of cluster membership for data.

How to access the help (after installing the package)

?DCEM
?dcem_test
?dcem_star_train
?dcem_train