Machine Learning, K-means Algorithm Implementation with R

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 09 Issue: 01 | Jan 2022 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 1268
Machine Learning, K-means Algorithm Implementation with R
Mrs. Kavita Ganesh Kurale1, Mrs. Rohini Sudhir Patil2
1Sr. Lecturer, Dept. of Computer Engineering, Sant Gajanan Maharaj Rural Polytechnic, Mahgaon,
Maharashtra,India.
2HOD, Dept. of Computer Engineering, Sant Gajanan Maharaj Rural Polytechnic, Mahgaon, Maharashtra, India.
---------------------------------------------------------------------***----------------------------------------------------------------------
ABSTRACT: Machine learning (ML) is that the growing
technology and scientific study of algorithms that enables
computers to find out automaticallyfrompreviousknowledge.
Machine learning uses numerous algorithms to create
mathematical models and makes predictions exploitation
previous knowledge available. Machine learning is artificial
intelligent application. Machine learning either supervised or
unsupervised learning. K-Means is most typically used
algorithm that is unsupervised learning algorithmic program
used for cluster analysis. During this paper we tend to worked
with the implementation of K-Means and R Programming.
Keywords: Machine Learning, K-means, R
Programming, supervised and unsupervised learning.
I. INTRODUCTION
Machine learning is one ofan applicationofartificial
intelligence (AI) .In Machine learning the systems can
automatically learn and improve the performance by using
previously calculated results Machine learning focuses on
implementation of new computer programs . It can access
data and use this data then learn new things and calculate
results.
The learning can be starts by observing knowledge,
using direct experience on previously used knowledge, or
instruction, and then patterns are calculated inthatdata and
make decisions in the future based on the examples. The
main aim is to allow the computers learn
automatically without manual interference and compute
results based on already computed results.
Some Machine Learning Methods
II. Classes of Machine Learning
1. Supervised Learning
2. Unsupervised Learning
Supervisedmachinelearning algorithms supervised
learning is a learning, we train the machine here some data
is given which is provided with the correct answer. After
that, the machine is provided with a new data set then
machine again forced work on that newly data set so that
supervised learning algorithm analyses the training data
set of training examples and produces a correct outcome
from sorted data. After sufficient training the system
provides targets for any new input. The learning algorithm
can also compare its output with the correct output and find
errors in order to modify the model accordingly.
In opposite to the present, unsupervised machine
learning algorithms are used when the knowledge used to
train is not classified or labeled The system doesn’t figure
out the right output; however it explores the knowledgeand
might draw inferences from datasets to describe hidden
structures from unlabeled data.
Semi-supervised machine learning algorithms fall
nearly in between supervised and unsupervised learning,
since they use both labeled and unlabeled data for training –
generally a small quantum of labeled data and a large
quantum of unlabeled data. The systems that use this
approach are suitable to considerably improve learning
accuracy. Generally, semi-supervised learning is chosen
when the acquired labeled data requires good and relevant
resources in order to train it/ learn from it. Else, acquiring
unlabeled data generally does not require additional
resources.
Reinforcement machine learning algorithms is a
learning approach that interacts with its environment by
producing actions and discovers breaches or rewards. Trial
and error search and delayedrewardarethemostapplicable
characteristics of reinforcement learning. In order to
maximize its performance this approach allows machines
and software agents to automatically determine the ideal
actions within a specific context. Simple price feedback is
needed for the agent to learn which action is stylish; this is
known as the underpinning signal. Machine learning
performs analysis of huge quantities of data. While it
generally delivers faster, more accurate results in order to
identify profitable opportunities or dangerous risks, it
should also require extra time and also resources to train it
properly. Combination of machine learning and AI and
cognitive technologies can turn it intoeffectivein processing
of large volumes of information.
III. Clustering
Clustering is the most popular approach in
unsupervised learning where data is grouped based on
the similarity of the datapoints. Clustering has
numerous real- life usages where it can be used in a
variety of situations. Clustering is used in colorful fields
like image recognition, pattern analysis, medical
informatics, genomics, data compression etc. in machine

learning this is part of the unsupervised learning
algorithm. This is because the datapoints present aren't
labeled and there's no explicit mapping of input and
outputs.
IV. K- MEANs Clustering
K-Means Clustering K- means is one of the
simplest unsupervised learning algorithms that answer
the well- known clustering problem. The procedure
follows an easy and straightforward Method to classify a
given data set through a particular number of clusters.
The main thing here is for every cluster; define k centers,
one for each. These centers should be placed during
a cunning way due to different position causes different
result. So, the better choice is to place them is important
as possible far away from each other. Figure below K-
Means Clustering. The next step is to take each data point
from a given data set and assign it to the nearest center.
When all data point completed, the primary step is
completed and an early group age is completed. At this
point we need tore-calculate k new centroids of the
clusters resulting from the previous step. (1)
The KMeans algorithm is very simple [3]:
1. Select the value of Initial centroids i.e. K.
2. Repeat step no 3 and step no 4 for all data points in
given dataset.
3. Find the closest data point from those centroids in
the Dataset.
4. Form K cluster. Clusters are formed by assigning
each point to its nearest centroid.
5. For each cluster in data set new global centroid are
computed.
K-means algorithm Properties[3]:
1. Efficient while processing large data set.
2. It works only on number values.
3. The clusters shape is convex.
Objective of the K-means
The objective of the K-means clustering is to
minimize the Euclideandistance that eachpointhasfromthe
centroid of the cluster.
Euclidean distance Formula
V. Implementation of K-Means with R-Programming
Step 1: Generation of Data
Here some random data is generated. Two vectors
are defined vector1 and vector2 and create a 2-D array
named data points which defines data points i.e. (x,y)
coordinate pairs.
> vector1 <- c(1, 1.5, 2, 2.5,3, 3.5, 4,4.5)
> vector2 <- c(1, 2, 3, 4,5,6,7,8)
> datapoints<-array(c(vector1,vector2), dim = c(8,2))
> print(datapoints)
The data Points defined here isa 2-Darray.Thefirst
column indicated the X coordinates, and the second column
represent Y-coordinates.
It is defined as shown below:
[,1] [,2]
[1,] 1.0 1
[2,] 1.5 2
[3,] 2.0 3
[4,] 2.5 4
[5,] 3.0 5
[6,] 3.5 6
[7,] 4.0 7
[8,] 4.5 8
Now in following diagram we plotted the data
points and visualize them using the plot function in R
programming. The output is shown as below:
>plot(datapoints)

Step 2: Initiate Random Centroids for k-Clusters
We will initialize 2 clusters with 2 centroids (1.5, 2) and
(3,5).
> k=2
> c1=c(1.5,2)
> c2=c(3,5)
> centroid=array(c(1.5,2,3,5), dim= c(k,2))
> print(centroid)
We define the k =2 number of clusters. An array of
two co-ordinate pairs is the centroids. the two clusters is
shown below is the array centroid containing the
coordinates :
[,1] [,2]
[1,] 1.5 3
[2,] 2.0 5
Using the plot function , We will plotthedata points
and the initial centroids on the same plot. We use
the points function to specify the centroids,.
The points function is used to highlight points of interest
using different colors. Centroids are represented using the
color red.
> plot(datapoints[,1], datapoints[,2])
>points(centroid[,1], centroid[,2], col="red")
Step 3: From each point Distance Calculation
Distance between the centroid and the remaining points are
calculated using Euclidean distance formula. The Euclidean
distance is defined as follows:
We will use the above equation above in the
following sub-section. Here we are calculated the Euclidean
distance formula in three steps.
Calculate the distance between thecorrespondingX
and Y coordinates of the data-points and the centroid.
Calculate the sum of the square of the differences computed
in Step 1.
Find the square root of the sum of squares ofdifferences
which is calculated in Step 2.
Difference: datapointi–centroid
dist_frm_clst1<-(datapoints[,]- centroid[1,])^2
> dist_frm_clst1=sqrt(dist_frm_clst1[,1]+ dist_frm_clst1[,2])
> dist_frm_clst1
[1] 0.7071068 1.8027756 1.5811388 1.11803403.8078866
3.0413813 6.0415230 [8] 5.2201533
Square of difference: (datapointi–centroid)2
>dist_frm_clst2=(datapoints[,]-centroid[2,])^2
Addition and Square root:
>dist_frm_clst2=sqrt(dist_frm_clst2[,1]+ dist_frm_clst2[,2])
> dist_frm_clst2
[1] 1.414214 4.609772 1.000000 2.692582 3.162278
1.802776 5.385165 3.041381
Here the dist_frm_clst1 is the distancewhichisbetween each
point and the centroid-1. Likewise , we calculate the
distances for centroid-2.
tot_dist=array(c(dist_frm_clst1,dist_frm_clst2),dim=c(8,2))
> tot_dist
[,1] [,2]
[1,] 0.7071068 1.414214
[2,] 1.8027756 4.609772
[3,] 1.5811388 1.000000
[4,] 1.1180340 2.692582
[5,] 3.8078866 3.162278

[6,] 3.0413813 1.802776
[7,] 6.0415230 5.385165
[8,] 5.2201533 3.041381
Step 4: Compare, finalize the Closest Centroids
Let’s create a logical comparing
vector dist_frm_clst_1 and dis_frm_clst2. This vector will be
made up of the Boolean values TRUE and FALSE. For
example create this vector using a conditional statement.
We write the condition as follows: distance to the first
cluster is less than the second cluster’s distance. Points here
that satisfy given condition belong to cluster 1. The
remaining points are belongs to cluster 2.
c(tot_dist[,1]<= tot_dist[,2])
[1] TRUE TRUE FALSE TRUE FALSE FALSE FALSE FALSE
Using the logical vector above, we obtain the
elements of the first cluster. The operation used below is an
example of conditional selection. Elements that satisfy this
condition in the array dataPoints are printed.
datapoints[,1][c(tot_dist[,1] <= tot_dist[,2])]
[1] 1.0 1.5 2.5
To find the centroid of the newly formed cluster, we
take the mean of all the points obtained above. The thinking
is as follows: We need to find a point closest to all the cluster
data points. Therefore, averaging the data points results ina
point closest to the remaining points.
>mean(datapoints[,1][c(tot_dist[,1] <= tot_dist[,2])])
We calculate the mean using the R
function mean. This is an exampleofhowweselect elements
conditionally that belongs to a cluster and how we find its
centroid.
[1] 1.666667
c1 = c(mean(datapoints[,1][c(tot_dist[,1] <=
tot_dist[,2])]),mean(datapoints[,2][c(tot_dist[,1] <=
tot_dist[,2])]))
We compute the X and Y coordinates of thecentroid
using the code above. We store the X coordinate in c1 and y-
coordinates in c2. We copy the data in these lists to a new
array called new_centroid.
> new_centroid[1,] = c1
> new_centroid[2,] = c2
The new_centroid contains the updated centroid of
the formed clusters. Therefore, we have implemented the
algorithm successfully.
> new_centroid
[,1] [,2]
[1,] 1.666667 2.333333
[2,] 3.400000 5.800000
Let’s plot the new centroids using the following
code:
plot(datapoints[,1], datapoints[,2])
> points(centroid[,1],centroid[,2],col="red")
>points(new_centroid[,1],new_centroid[,2],col="green")
The old and updated centroids are shown in the
figure below.
VI. CONCLUSION
Kmeans clustering is one of the most popular and
widely used clustering algorithms, usually the apply
when solving clustering tasks to get an idea of the
structure of the dataset. The main aim of kmeans
algorithm is to group data points into distinct non-
overlapping subgroups such that single group contain
same type of data item. Here we implemented Kmeans
algorithm using r-programming and computed new
global centroid for clusters successfully. Data is
generated using vector in r and Euclidean distance
formula is used for distance calculation. We calculated
distance using mean function in r and new centroid
plotted on graph. Hence we followed all K means
algorithm steps for centroid computation
REFERENCES
[1] International Journal of Pure and Applied Mathematics
Volume 117 No. 7 2017, 157-164 ISSN: 1311-8080 (printed
version); ISSN: 1314-3395 (on-line version) url:
http://www.ijpam.eu Special Issue “A k-means Clustering
Algorithm on Numeric Data”
[2] International Journal of Information & Computation
Technology. ISSN 0974-2239 Volume 4, Number 17 (2014),

pp. 1847-1860 © International ResearchPublicationsHouse
http://www. Irphouse.com A Review ON K-means DATA
Clustering APPROACH
[3] 2017 6th International Conference on Reliability,
Infocom Technologies and Optimization (ICRITO) (Trends
and Future Directions), Sep. 20-22, 2017, AIIT, Amity
University Uttar Pradesh, Noida, India “A Detailed Study of
Clustering Algorithms”
[4] https://data-flair.training/blogs/using-r-for-data-
science/

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