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5 Clustering methods in R

2/15/2018

Machine Learning Specialization from University of Washington

Clustering is a way of grouping a set of objects into clusters or groups such that object in each group have similar characteristics. R has many methods of clustering and each method helps to cluster the objects according to certain parameters. 5 methods of clustering discussed in this article are:

K-means
K-medoids /PAM Clustering
Hierarchical Clustering
Hierarchical K-means Clustering and
Model Based Clustering

Clustering Methods in R

Data for clustering

library(rattle)

#Input wine data from rattle package
data(wine,package = 'rattle')

head(wine)

##   Type Alcohol Malic  Ash Alcalinity Magnesium Phenols Flavanoids
## 1    1   14.23  1.71 2.43       15.6       127    2.80       3.06
## 2    1   13.20  1.78 2.14       11.2       100    2.65       2.76
## 3    1   13.16  2.36 2.67       18.6       101    2.80       3.24
## 4    1   14.37  1.95 2.50       16.8       113    3.85       3.49
## 5    1   13.24  2.59 2.87       21.0       118    2.80       2.69
## 6    1   14.20  1.76 2.45       15.2       112    3.27       3.39
##   Nonflavanoids Proanthocyanins Color  Hue Dilution Proline
## 1          0.28            2.29  5.64 1.04     3.92    1065
## 2          0.26            1.28  4.38 1.05     3.40    1050
## 3          0.30            2.81  5.68 1.03     3.17    1185
## 4          0.24            2.18  7.80 0.86     3.45    1480
## 5          0.39            1.82  4.32 1.04     2.93     735
## 6          0.34            1.97  6.75 1.05     2.85    1450

#Scale the variables to standard format
wine_scaled<-scale(wine[-1])

Determine the optimal number of clusters

wssplot <- function(data, nc=15, seed=1234){
  wss <- (nrow(data)-1)*sum(apply(data,2,var))
  for (i in 2:nc){
    set.seed(seed)
    wss[i] <- sum(kmeans(data, centers=i)$withinss)}
  plot(1:nc, wss, type="b", xlab="Number of Clusters",
       ylab="Within groups sum of squares")}

wssplot(wine_scaled, nc=6)

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Different methods of Cluster analysis in R

1) K-Means

kmeans_fit<-kmeans(wine_scaled,3) # 3 is the optimal number for k

#Clustering attributes of the kmeans-fit
attributes(kmeans_fit)

## $names
## [1] "cluster"      "centers"      "totss"        "withinss"    
## [5] "tot.withinss" "betweenss"    "size"         "iter"        
## [9] "ifault"      
## 
## $class
## [1] "kmeans"

#Centeroids of kmeans-fit
kmeans_fit$centers

##      Alcohol      Malic        Ash Alcalinity   Magnesium     Phenols
## 1  0.8328826 -0.3029551  0.3636801 -0.6084749  0.57596208  0.88274724
## 2  0.1644436  0.8690954  0.1863726  0.5228924 -0.07526047 -0.97657548
## 3 -0.9234669 -0.3929331 -0.4931257  0.1701220 -0.49032869 -0.07576891
##    Flavanoids Nonflavanoids Proanthocyanins      Color        Hue
## 1  0.97506900   -0.56050853      0.57865427  0.1705823  0.4726504
## 2 -1.21182921    0.72402116     -0.77751312  0.9388902 -1.1615122
## 3  0.02075402   -0.03343924      0.05810161 -0.8993770  0.4605046
##     Dilution    Proline
## 1  0.7770551  1.1220202
## 2 -1.2887761 -0.4059428
## 3  0.2700025 -0.7517257

#Aggregate the number of clusters by means
aggregate(wine_scaled,by=list(kmeans_fit$cluster),FUN=mean)

##   Group.1    Alcohol      Malic        Ash Alcalinity   Magnesium
## 1       1  0.8328826 -0.3029551  0.3636801 -0.6084749  0.57596208
## 2       2  0.1644436  0.8690954  0.1863726  0.5228924 -0.07526047
## 3       3 -0.9234669 -0.3929331 -0.4931257  0.1701220 -0.49032869
##       Phenols  Flavanoids Nonflavanoids Proanthocyanins      Color
## 1  0.88274724  0.97506900   -0.56050853      0.57865427  0.1705823
## 2 -0.97657548 -1.21182921    0.72402116     -0.77751312  0.9388902
## 3 -0.07576891  0.02075402   -0.03343924      0.05810161 -0.8993770
##          Hue   Dilution    Proline
## 1  0.4726504  0.7770551  1.1220202
## 2 -1.1615122 -1.2887761 -0.4059428
## 3  0.4605046  0.2700025 -0.7517257

#Append Cluster to data

wine<-data.frame(wine,Cluster=kmeans_fit$cluster)
head(wine)

##   Type Alcohol Malic  Ash Alcalinity Magnesium Phenols Flavanoids
## 1    1   14.23  1.71 2.43       15.6       127    2.80       3.06
## 2    1   13.20  1.78 2.14       11.2       100    2.65       2.76
## 3    1   13.16  2.36 2.67       18.6       101    2.80       3.24
## 4    1   14.37  1.95 2.50       16.8       113    3.85       3.49
## 5    1   13.24  2.59 2.87       21.0       118    2.80       2.69
## 6    1   14.20  1.76 2.45       15.2       112    3.27       3.39
##   Nonflavanoids Proanthocyanins Color  Hue Dilution Proline Cluster
## 1          0.28            2.29  5.64 1.04     3.92    1065       1
## 2          0.26            1.28  4.38 1.05     3.40    1050       1
## 3          0.30            2.81  5.68 1.03     3.17    1185       1
## 4          0.24            2.18  7.80 0.86     3.45    1480       1
## 5          0.39            1.82  4.32 1.04     2.93     735       1
## 6          0.34            1.97  6.75 1.05     2.85    1450       1

#Size of the cluster
kmeans_fit$size

## [1] 62 51 65

#Evaluate the Clustering accuracy using a confusion matrix
confusion_matrix_table<-table(wine[,1],kmeans_fit$cluster)
library(caret)
confusionMatrix(confusion_matrix_table)

## Confusion Matrix and Statistics
## 
##    
##      1  2  3
##   1 59  0  0
##   2  3  3 65
##   3  0 48  0
## 
## Overall Statistics
##                                           
##                Accuracy : 0.3483          
##                  95% CI : (0.2786, 0.4232)
##     No Information Rate : 0.3652          
##     P-Value [Acc > NIR] : 0.7053          
##                                           
##                   Kappa : 0.0299          
##  Mcnemar's Test P-Value : NA              
## 
## Statistics by Class:
## 
##                      Class: 1 Class: 2 Class: 3
## Sensitivity            0.9516  0.05882   0.0000
## Specificity            1.0000  0.46457   0.5752
## Pos Pred Value         1.0000  0.04225   0.0000
## Neg Pred Value         0.9748  0.55140   0.5000
## Prevalence             0.3483  0.28652   0.3652
## Detection Rate         0.3315  0.01685   0.0000
## Detection Prevalence   0.3315  0.39888   0.2697
## Balanced Accuracy      0.9758  0.26170   0.2876

#Cluster visualization

#1) Cluster Plot
library(cluster)
clusplot(wine_scaled, kmeans_fit$cluster, main='2D representation of the Cluster solution',color=TRUE, shade=TRUE,labels=2, lines=0)

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#2)Using package factoextra
library(factoextra)

fviz_cluster(kmeans_fit,data = wine_scaled,ellipse.type = "convex",palette="jco",ggtheme = theme_minimal())

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2)K-medoids/PAM Clustering

pam_fit<-pam(wine_scaled,3)

#Visualization using Factoextra
fviz_cluster(pam_fit,data = wine_scaled,ellipse.type = "convex",palette="jco",ggtheme = theme_minimal())

plot of chunk unnamed-chunk-4

3)Hierarchical Clustering

#Eucledian Distance Matrix
distance<-dist(wine_scaled,method = "euclidean")

#Model for hierchical clustering
hierach_fit<-hclust(distance,method = "ward.D2")

# Simple Plot
plot(hierach_fit)

# Rectangular plot with groups 
groups<-cutree(hierach_fit,k=3) # Cutting the dendrogram into 3 groups

rect.hclust(hierach_fit,k=3,border = "red")

plot of chunk unnamed-chunk-5

#Visualize using factoextra

# Cut in 4 groups and color by groups
fviz_dend(hierach_fit, k = 4, # Cut in four groups
          cex = 0.5, # label size
          k_colors = c("#2E9FDF", "#00AFBB", "#E7B800", "#FC4E07"),
          color_labels_by_k = TRUE, # color labels by groups
          rect = TRUE # Add rectangle around groups
          )

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#Evaluate the accuarcy of model with confusion matrix

table(wine[,1],groups)

##    groups
##      1  2  3
##   1 59  0  0
##   2  5 58  8
##   3  0  0 48

4)Hierarchical K-means Clustering

hierach_kmeans_fit<-hkmeans(wine_scaled,4)

hierach_kmeans_fit

## Hierarchical K-means clustering with 4 clusters of sizes 59, 36, 51, 32
## 
## Cluster means:
##      Alcohol      Malic        Ash Alcalinity   Magnesium    Phenols
## 1  0.9028300 -0.2969818  0.2925626 -0.6927815  0.55567318  0.8917585
## 2 -0.8903875 -0.4346029 -1.1132218 -0.3153936 -0.50507989  0.2266227
## 3  0.1644436  0.8690954  0.1863726  0.5228924 -0.07526047 -0.9765755
## 4 -0.9249888 -0.3486324  0.4159309  0.7987738 -0.33636118 -0.3427131
##    Flavanoids Nonflavanoids Proanthocyanins      Color        Hue
## 1  0.95147729    -0.6073179       0.5966082  0.1931051  0.4694211
## 2  0.22876921    -0.6019082       0.3279625 -0.8411535  0.3927557
## 3 -1.21182921     0.7240212      -0.7775131  0.9388902 -1.1615122
## 4 -0.08029881     0.6429805      -0.2297927 -0.9060961  0.5438146
##      Dilution    Proline
## 1  0.77491047  1.1750720
## 2  0.47415842 -0.7144213
## 3 -1.28877614 -0.4059428
## 4  0.09181759 -0.7158436
## 
## Clustering vector:
##   [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 4 1 1 1 1 1 1 1 1 1
##  [36] 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 4 3 2 2 4 4 2 2 4 2
##  [71] 4 4 4 1 2 2 2 4 2 4 2 2 4 3 2 2 4 4 4 4 4 4 4 2 2 1 4 2 2 2 2 2 4 2 2
## [106] 4 2 4 2 2 2 2 4 4 4 4 2 4 3 2 2 4 4 2 2 2 2 4 4 4 3 3 3 3 3 3 3 3 3 3
## [141] 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
## [176] 3 3 3
## 
## Within cluster sum of squares by cluster:
## [1] 322.0013 273.4497 326.3537 252.2581
##  (between_SS / total_SS =  49.0 %)
## 
## Available components:
## 
##  [1] "cluster"      "centers"      "totss"        "withinss"    
##  [5] "tot.withinss" "betweenss"    "size"         "iter"        
##  [9] "ifault"       "data"         "hclust"

# Visualize the dendrogram tree

fviz_dend(hierach_kmeans_fit, cex = 0.6, palette = "jco", 
          rect = TRUE, rect_border = "jco", rect_fill = TRUE)

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# Visualize the clusters

fviz_cluster(hierach_kmeans_fit, palette = "jco", repel = TRUE,
             ggtheme = theme_classic())

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5) Model Based Clustering

library(mclust)

mclust_fit<- Mclust(wine_scaled)

#Summary of the model

summary(mclust_fit)

## ----------------------------------------------------
## Gaussian finite mixture model fitted by EM algorithm 
## ----------------------------------------------------
## 
## Mclust VVE (ellipsoidal, equal orientation) model with 3 components:
## 
##  log.likelihood   n  df       BIC     ICL
##       -2285.363 178 158 -5389.448 -5390.9
## 
## Clustering table:
##  1  2  3 
## 56 73 49

# Plot using facto extra

# BIC values used for choosing the number of clusters
fviz_mclust(mclust_fit, "BIC", palette = "jco")

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# Classification: plot showing the clustering
fviz_mclust(mclust_fit, "classification", geom = "point", 
            pointsize = 1.5, palette = "jco")

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# Classification uncertainty
fviz_mclust(mclust_fit, "uncertainty", palette = "jco")

plot of chunk unnamed-chunk-7

1 Comment

5 Clustering methods in R

Clustering Methods in R

Data for clustering

Determine the optimal number of clusters

Different methods of Cluster analysis in R

1) K-Means

2)K-medoids/PAM Clustering

3)Hierarchical Clustering

4)Hierarchical K-means Clustering

5) Model Based Clustering

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