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How Can Big Data Tools Complement a Data Warehouse?

Posted on July 25, 2018May 23, 2020 by Dexlab

How Can Big Data Tools Complement a Data Warehouse?

Every person believes that he/she is above average. Businesses feel the same way about their best asset— data. They want to believe that their big data is above average and perfect for implementing advanced big data tools. But, that’s not the case always.

Do you really need big data tools?

In the data world, big data tools like Hadoop Spark and NoSQL are like freight trains delivering goods. Freight trains are powerful, but they’ve limited routes and a slow start. They are great for delivering goods in bulk regularly. However, if you need a swift delivery, freight train might not be the best choice.

So firs of all, it is important to understand if there’s a big data scenario in your business or not.

A 100 times increase in data velocity, volume or variety indicates that you have a big data situation at hand. For example, if data velocity increases to hundreds of thousands of transactions per hour from thousands of transactions, or if the data sources shoot up from dozens to hundreds, you can safely conclude that your business is dealing with big data.

In such scenarios, you are likely to get frustrated with traditional SQL tools. A complete revamp or moderate tuning of existing big data tools is needed to effectively handle such massive data sets.

What tools to use?

The tool to be used depends on the task at hand. For main business outcomes like sales, payments, etc., traditional reporting tools employed within the data warehouse architecture are suitable. For secondary business outcomes like following the customer journey in detail, tracking browsing history and monitoring device activity, big data tools within data warehouse are necessary. In a data warehouse these events are aggregated into models that show the summarized business processes.

Incorporating Big Data Tools in Data Warehouse

Consider an alarm company with sensors that are connected though the internet across an entire country. Storing the response of individual sensors in a SQL data warehouse would incur huge expenses, but no value. An alternative storage solution is retaining this information in data lake environments that are cheaper and later aggregating them in a data warehouse. For example, the company could define sensor events that constitute a person locking up a house. A fact table recording departures and arrivals could be stoked up in a data warehouse as an aggregate event.

There are many other use cases. Some are given below:

Sum up and filter IoT data: A leading bed manufacturing company uses biometric sensors in their range of luxury mattresses. Apache Hadoop could be used to store individual sensor readings and Apache Spark can be employed to amass and filter signals. The aggregated data in data warehouses can be used to create time-trended reports once the boundary metrics are surpassed.

Merge real-time data with past data: Financial institutes need live access to market data. However, they also need to store that data and use it for identifying historical trends in future. Merging these two types of data with tools like Apache Kafka or Amazon Kinesis is important because, with these tools the data can be directly streamed to visualization tools and there’s hardly any delay.

The ultimate goal is to form a balance between the two sides of the data pipeline. While it is important to collect as much raw data about customers as possible, it is equally important to use the right tool for the right job.

To read more blogs on the latest developments in the field of big data, follow DexLab Analytics. We are a premier Hadoop training institute in Gurgaon. To aid your big data dreams, we have started a new admission drive #BigDataIngestion where we offer flat 10% discount to all students interested in our big data Hadoop courses. Enroll now!

Reference: https://tdwi.org/articles/2018/07/20/arch-all-5-use-cases-integrating-big-data-tools-with-data-warehouse.aspx

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Top 5 Up-And-Coming Big Data Trends for 2018

Posted on July 19, 2018May 23, 2020 by Dexlab

Top 5 Up-And-Coming Big Data Trends for 2018

The big data market is constantly growing and evolving. It is predicted that by 2020 there will be over 400,000 big data jobs in the US alone, but only around 300,000 skilled professionals in the field. The constant evolution of the big data industry makes it quite difficult to predict trends. However, below are some of the trends that are likely to take shape in 2018.

Open source frameworks:

Open source frameworks like Hadoop and Spark are dominating the big data realm for quite some time now and this trend will continue in 2018. The use of Hadoop is increasing by 32.9% every year- according to Forrester forecast reports. Experts say that 2018 will see an increase in the usage of Hadoop and Spark frameworks for better data processing by organizations. As per TDWI Best Practices report, 60% of enterprises aim to have Hadoop clusters functioning in production by end of 2018.

As Hadoop frameworks are becoming more popular, companies are looking for professionals skilled in Hadoop and similar techs so that they can draw valuable insights from real-time data. Owing to these reasons, more and more candidates interested to make a career in this field are going for big data Hadoop training.

Visualization Models:

A survey was conducted with 2800 BI experts in 2017 where they highlighted the importance of data discovery and data visualization. Data discovery isn’t just about understanding, analyzing and discovering patterns in the data, but also about presenting the analysis in a manner that easily conveys the core business insights. Humans find it simpler to process visual patterns. Hence, one of the significant trends of 2018 is development of compelling visualization models for processing big data.

Streaming success:

Every organization is looking to master streaming analytics- a process where data sets are analyzed while they are still in the path of creation. This removes the problem of having to replicate datasets and provides insights that are up-to-the-second. Some of the limitations of streaming analytics are restricted sizes of datasets and having to deal with delays. However, organizations are working to overcome these limitations by end of 2018.

Dark data challenge

Dark data refers to any kind of data that is yet to be utilized and mainly includes non-digital data recording formats such as paper files, historical records, etc. the volume of data that we generate everyday may be increasing, but most of these data records are in analog form or un-digitized form and aren’t exploited through analytics. However, 2018 will see this dark data enter cloud. Enterprises are coming up with big data solutions that enable the transfer of data from dark environments like mainframes into Hadoop.

Enhanced efficiency of AI and ML:

Artificial intelligence and machine learning technologies are rapidly developing and businesses are gaining from this growth through use cases like fraud detection, pattern recognition, real-time ads and voice recognition. In 2018, machine learning algorithms will go beyond traditional rule-based algorithms. They will become speedier and more precise and enterprises will use these to make more accurate predictions.

These are some of the top big data trends predicted by industry experts. However, owing to the constantly evolving nature of big data, we should brace ourselves for a few surprises too!

Big data is shoving the tech space towards a smarter future and an increasing number of organizations are making big data their top priority. Take advantage of this data-driven age and enroll for big data Hadoop courses in Gurgaon. At DexLab Analytics, industry-experts patiently teach students all the theoretical fundamentals and give them hands-on training. Their guidance ensures that students become aptly skilled to step into the world of work. Interested students can now avail flat 10% discount on big data courses by enrolling for DexLab’s new admission drive #BigDataIngestion.

Reference: https://www.analyticsinsight.net/emerging-big-data-trends-2018

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Step-by-step Guide for Implementation of Hierarchical Clustering in R

Posted on July 17, 2018July 17, 2018 by Dexlab

Step-by-step Guide for Implementation of Hierarchical Clustering in R

Hierarchical clustering is a method of clustering that is used for classifying groups in a dataset. It doesn’t require prior specification of the number of clusters that needs to be generated. This cluster analysis method involves a set of algorithms that build dendograms, which are tree-like structures used to demonstrate the arrangement of clusters created by hierarchical clustering.

It is important to find the optimal number of clusters for representing the data. If the number of clusters chosen is too large or too small, then the precision in partitioning the data into clusters is low.

NbClust

The R package NbClust has been developed to help with this. It offers good clustering schemes to the user and provides 30 indices for determining the number of clusters.

Through NbClust, any combination of validation indices and clustering methods can be requested in a single function call. This enables the user to simultaneously evaluate several clustering schemes while varying the number of clusters.

One such index used for getting optimum number of clusters is Hubert Index.

Performing Hierarchical Clustering in R

In this blog, we shall be performing hierarchical clustering using the dataset for milk. The flexclust package is used to extract this dataset.

The milk dataset contains observations and parameters as shown below:

As seen in the dataset, milk obtained from various animal sources and their respective proportions of water, protein, fat, lactose and ash have been mentioned.

For making calculations easier, we scale down original values into a standard normalized form. For that, we use processes like centering and scaling. The variable may be scaled in the following ways:

Subtract mean from each value (centering) and then divide it by standard deviation or divide it by its mean deviation about mean (scaling)

Divide each value in the variable by maximum value of the variable

After scaling the variables we get the following matrix

The next step is to calculate the Euclidean distance between different data points and store the result in a variable.

Hierarchical average linkage method is used for performing clustering of different animal sources. The formula used for that is shown below.

We obtain 25 clusters from the dataset.

To draw the dendogram we use the plot command and we obtain the figure given below.

The Nbclust library is used to get the optimum number of clusters for partitioning the data. The maximum and minimum number of clusters that is needed is stored in a variable. The nbClust method finds out the optimum number of clusters according to different clustering indices and finally the Hubert Index decides the optimum value of the number of clusters.

The optimum cluster value is 3, as can be seen in the figure below.

Values corresponding to knee jerk visuals in the graph give the number of clusters needed.

The graph shows that the maximum votes from various clustering indices went to cluster 3. Hence, the data is partitioned into 3 clusters.

The graph is partitioned into 3 clusters as shown by the red lines.

Now, the points are portioned into 3 clusters as opposed to the 25 clusters we got initially.

Next, the clusters are assigned to the observations.

The clusters are assigned different colors for ease of visualization

That brings us to a close on the topic of Hierarchical clustering. In the upcoming blogs, we shall be discussing K-Means clustering. So, follow DexLab Analytics – a leading institute providing big data Hadoop training in Gurgaon. Enroll for their big data Hadoop courses and avail flat 10% discount. To more about this #SummerSpecial offer, visit our website.

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Study: Demand for Data Scientists is Sky-Rocketing; India Leads the Show

Posted on July 16, 2018December 2, 2019 by Dexlab

Study: Demand for Data Scientists is Sky-Rocketing; India Leads the Show

Last year, India witnessed a surging demand for data scientists by more than 400% – as medium to large-scale companies are increasingly putting their faith on data science capabilities to build and develop next generation products that will be well integrated, highly personalized and extremely dynamic.

Companies in the Limelight

At the same time, India contributed to almost 10% of open job openings for data scientists worldwide, making India the next data science hub after the US. This striking revelation comes at a time when Indian IT sector job creation has hit a slow mode, thus flourishing data science job creation is found providing a silver lining. According to the report, Microsoft, JPMorgan, Deloitte, Accenture, EY, Flipkart, Adobe, AIG, Wipro and Vodafone are some of the top of the line companies which hired the highest number of data scientists this year. Besides data scientists, they also advertised openings for analytics managers, analytics consultants and data analysts among others.

City Stats

After blue chip companies, talking about Indian cities which accounts for the most number of data scientists – we found that Bengaluru leads the show with highest number of data analytics and science related jobs accounting for almost 27% of the total share. In fact, the statistics has further increased from the last year’s 25%, followed by Delhi NCR and Mumbai. Even, owing to an increase in the number of start-ups, 14% of job openings were posted from Tier-II cities.

Notable Sectors

A large chunk of data science jobs originated from the banking and financial sector – 41% of job generation was from banking sector. Other industries that followed the suit are Energy & Utilities and Pharmaceutical and Healthcare; both of which have observed significant increase in job creation over the last year.

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Talent Supply Index (TSI) – Insights

Another study – Talent Supply Index (TSI) by Belong suggested that the demand in jobs is a result of data science being employed in some areas or the other across industries with burgeoning online presence, evident in the form of targeted advertising, product recommendation and demand forecasts. Interestingly, businesses sit on a massive pile of information collected over years in forms of partners, customers and internal data. Analyzing such massive volumes of data is the key.

Shedding further light on the matter, Rishabh Kaul, Co-Founder, Belong shared, “If the TSI 2017 data proved that we are in a candidate-driven market, the 2018 numbers should be a wakeup call for talent acquisition to adopt data-driven and a candidate-first approach to attract the best talent. If digital transformation is forcing businesses to adapt and innovate, it’s imperative for talent acquisition to reinvent itself too.”

Significantly, skill-based recruitment is garnering a lot of attention of the recruiters, instead of technology and tool-based training. The demand for Python skill is the highest scoring 39% of all posted data science and analytical jobs. In the second position is R skill with 25%.

Last Notes

The analytics job landscape in India is changing drastically. Companies are constantly seeking worthy candidates who are well-versed in particular fields of study, such as data science, big data, artificial intelligence, predictive analytics and machine learning. In this regard, this year, DexLab Analytics launches its ultimate admission drive for prospective students – #BigDataIngestion. Get amazing discounts on Big Data Hadoop training in Gurgaon and promote an intensive data culture among the student fraternity.

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For a Seamless, Real-Time Integration and Access across Multiple Data Siloes, Big Data Fabric Is the Solution

Posted on June 28, 2018June 28, 2018 by Dexlab

For a Seamless, Real-Time Integration and Access across Multiple Data Siloes, Big Data Fabric Is the Solution

Grappling with diverse data?

No worries, data fabrics for big data is right here.

The very notion of a fabric joining computing resources and offering centralized access to a set of networks has been doing rounds since the conceptualization of grid computing as early as 1990s. However, a data fabric is a relatively new concept based on the same underlying principle, but it’s associated with data instead of a system.

As data have become increasingly diversified, the importance of data fabrics too spiked up. Now, integrating such vast pools of data is quite a problem, as data collected across various channels and operations is often withhold in discrete silos. The responsibility lies within the enterprise to bring together transactional data stores, data lakes, warehouses, unstructured data sources, social media storage, machine logs, application storage and cloud storage for management and control.

The Change That Big Data Brings In

The escalating use of unstructured data resulted in significant issues with proper data management. While the accuracy and usability quotient remained more or less the same, the ability to control them has been reduced because of increasing velocity, variety, volume and access requirements of data. To counter the pressing challenge, companies have come with a number of solutions but the need for a centralized data access system prevails – on top of that big data adds concerns regarding data discovery and security that needs to be addressed only through a particular single access mechanism.

To taste success with big data, the enterprises need to seek access to data from a plethora of systems in real time in perfectly digestible formats – also connecting devices, including smartphones and tablets enhances storage related issues. Today, big data storage is abundantly available in Apache Spark, Hadoop and NoSQL databases that are developed with exclusive management demands.

The Popularity of Data Fabrics

Huge data and analytics vendors are the biggest providers of big data fabric solutions. They help offer access to all kinds of data and conjoin them into a single consolidated system. This consolidated system – big data fabric – should tackle diverse data stores, nab security issues, offer consistent management through unified APIs and software access, provide auditability, flexibility and be upgradeable and process smooth data ingestion, curation and integration.

With the rise of machine learning and artificial intelligence, the requirements of data stores increase as they form the fundamentals of model training and operations. Therefore, enterprises are always seeking a single platform and a single point for data access, they tend to reduce the intricacies of the system and ensure easy storage of data. Not only that, data scientists no longer need to focus on the complexities of data access, rather they can give their entire attention to problem-solving and decision-making.

To better understand how data fabrics provide a single platform and a single point for data access across myriad siloed systems, you need a top of the line big data certification today. Visit DexLab Analytics for recognized and well-curated big data hadoop courses in Gurgaon.

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Referenes: https://tdwi.org/articles/2018/06/20/ta-all-data-fabrics-for-big-data.aspx

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An ABC of Apache Spark Streaming

Posted on June 26, 2018 by Dexlab

Estimator Procedure under Simple Random Sampling: EXPLAINED

Apache Spark has become one the most popular technologies. It is accompanied with a powerful streaming library, which has quite a few advantages over other technologies. The integration of Spark streaming APIs with Spark core APIs provides a dual purpose real-time and batch analytical platform. Spark Streaming can also be combined with SparkSQL, SparkML and GraphX when complex cases need to be handled. Famous organizations that prevalently use Spark Streaming are Netflix, Uber and Pinterest. Spark Streaming’s fame in the world of data analytics can be attributed to its fault tolerance, ability to process live streams, scalability and high throughput.

Need for Streaming Analytics:

Companies generate enormous amounts of data on a daily basis. Transactions happening over the internet, social network platforms, IoT devices, etc. generate large volumes of data that need to be leveraged in real-time. And this process shall gain more important in future. Entrepreneurs consider real-time data analysis as a great opportunity to scale up their businesses.

Spark streaming intakes live data streams, Spark engine processes and divides it and the output is in the form of batches.

Architecture of Spark Streaming:

Spark streaming breaks the data stream into micro batches (known as discretize stream processing). First of all, the receivers accept data in parallel and hold it in worker nodes as buffer. Then the engine runs brief tasks and sends the result to other systems.

Spark tasks are allocated to workers dynamically, that depends on the resources available and the locality of data. The advantages of Spark Streaming are many, including better load balancing and speedy fault recovery. Resilient distributed dataset (RDD) is the basic concept behind fault tolerant datasets.

Useful features of Spark streaming:

Easy to use: Spark streaming supports Java, Scala and Python and uses the language integrated API of Apache Spark for stream processing. Stream jobs can be written in a similar manner in which batch jobs are written.

Spark Integration: Since Spark streaming runs on Spark, it can be utilized for addressing unplanned queries and reusing similar codes. Robust interactive applications can also be designed.

Fault tolerance: Work that has been lost can be recovered without additional coding from the developer.

Benefits of discretized stream processing:

Load balancing: In Spark streaming, the job load is balanced across workers. While, some workers handle more time-consuming tasks, others process tasks that take less time. This is an improvement from traditional approaches where one task is processed at a time. This is because if the task is time-taking then it behaves like a bottle neck and delays the whole pipeline.

Fast recovery: In many cases of node failures, the failed operators need to be restarted on different nodes. Recomputing lost information involves rerunning a portion of the data stream. So, the pipeline gets halted until the new node catches up after the rerun. But in Spark, things work differently. Failed tasks can be restarted in parallel and the recomputations are distributed across different nodes evenly. Hence, recovery is much faster.

Spark streaming use cases:

Uber: Uber collects gigantic amounts of unstructured data from mobile users on a daily basis. This is converted to structured data and sent for real time telemetry analysis. This data is analyzed in an ETL pipeline build using Spark streaming, Kafka and HDFS.

Pinterest: To understand how Pinterest users are engaging with pins globally, it uses an ETL data pipeline to provide information to Spark through Spark streaming. Hence, Pinterest aces the game of showing related pins to people and providing relevant recommendations.

Netflix: Netflix relies on Spark streaming and Kafka to provide real-time movie recommendations to users.

Apache foundation has been inaugurating new techs, such as Spark and Hadoop. For performing real-time analytics, Spark streaming is undoubtedly one of the best options.

As businesses are swiftly embracing Apache Spark with all its perks, you as a professional might be wondering how to gain proficiency in this promising tech. DexLab Analytics, one of the leading Apache Spark training institutes in Gurgaon, offers expert guidance that is sure to make you industry-ready. To know more about Apache Spark certification courses, visit Dexlab’s website.

This article has been sources from: https://intellipaat.com/blog/a-guide-to-apache-spark-streaming-tutorial

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Estimator Procedure under Simple Random Sampling: EXPLAINED

Posted on June 26, 2018May 23, 2020 by Dexlab

Estimator Procedure under Simple Random Sampling: EXPLAINED

In continuation with the previous introductory blog on sampling: An ABC Guide to Sampling Theory, we will take a closer look into the concept of the estimator procedure under Simple Random Sampling with the help of mathematical examples. It will help us understand the underlying phenomenon, the manner to be precise in which the estimator function of sampling works.

Simple random sampling (SRS) is a method of selecting a sample comprising ‘n’ number of sampling units out of the population of ‘N’ number of sampling units such that every sampling unit has an equal chance of being chosen.

The Estimator Procedure under Simple Random Sampling

The process of selection of a sample under SRS (Simple Random Sampling) is random. This means, each number of the population has an equal probability of getting selected, which makes each of the observation identical and independently distributed.

The statistic chosen by the investigation of estimation of random samples need to satisfy a set of certain properties given below:

Unbiasedness
Consistency
Sufficiency
Efficiency

As a matter of fact, investigation is always about coming up with an idea regarding the population parameters based on the sample observations. The best part would be to formulate an unbiased, consistent estimator, which is also efficient. Normally, a sample mean for a set of sample observations is considered to be a very desirable estimator to form ideas about population parameters.

In detail, let’s examine the relevance of each of the properties of an estimator:

Unbiasedness of an estimator

Take a look at the below examples to understand the very idea of unbiasedness.

Example 1:

Answer:-

According to the problem, we have

Adding (1) & (2), we get,

So, from (3), we get:-

is called an unbiased estimators for .

Now, subtracting (2) & (1), we get –

Example 2:

Assume that an investigator draws a sample from this population using SRSWR. Then show that the sample mean is an unbiased estimator for the population mean.

Now, by specification we have:-

We are redefined to show that:-

L.H.S :

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Hadoop or Spark: Which Big Data Framework to Choose?

Posted on June 25, 2018May 23, 2020 by Dexlab

Hadoop or Spark: Which Big Data Framework to Choose?

Feeling confused?

Of late, Spark has overtaken Hadoop for being the most active open source big data project. Though they have their differences, they both have many common uses.

To begin, they both are incredible big data frameworks. For some years, Hadoop has been leading the open source big data framework clusters but recently highly advanced Spark tends to have captured the market. The latter has become increasingly popular and for all the right reasons. But that is not to say, Hadoop is losing its significance entirely.

They don’t perform exactly the similar tasks. Neither are they mutually exclusive. Though it’s been heard that Spark can work 100X faster than Hadoop in some scenarios, it doesn’t come with its own distributed storage system, which is quite fundamental to big data projects. Distributed storage offers elaborate multi-petabyte dataset storage solution across almost infinite number of computer hard drives. As compared to expensive machinery customization which holds everything in one device, distributed system is cheap as well as scalable, which means as many devices can be added if the network of data set ever grows.

Moreover, Spark doesn’t have its own file system; it cannot organize files in a distributed way without help from third party. This is the reason why several companies think of installing Spark after Hadoop, so that superior analytical applications of Spark can employ data stored using HDFS.

So, what makes Spark win over Hadoop? It’s the SPEED. Spark is a champion of handling a large chunk of its operations ‘in memory’- this reduces a lot of time and effort, indeed. Thanks to MapReduce!

MapReduce writes of the data right to its physical storage medium after each activity. The main purpose of this was to ensure a fully recovery if something goes wrong – nevertheless, Spark organizes data in Resilient Distributed Datasets, where data can be easily recovered following failure or any kind of mishap.

The main driving factor behind growth of Spark lies in its adept functionality for tackling advanced data processing tasks, including machine learning and real-time stream processing. Real-time processing stands for feeding data into analytical applications the moment it’s seized, and insights are right away directed back to the users through a dashboard to inspire action. This kind of processing is nowadays very much used in big data, thus making Spark enjoy an upper hand against its Hadoop counterpart.

The technology of machine learning is right at the kernel of digital revolution – artificial intelligence and creating far-fetched algorithms is an area of analytics Spark excels at. Its speed and the sound capability to tackle streaming data are the reasons behind. Spark has its own machine learning libraries, known as MLib, while Hadoop needs to collaborate with third-party machine learning library, for example Apache Mahout.

As closing thoughts, though it appears that the two big data frameworks are stiff competitors of each other, yet this is really not the case in the reality. The corporate uses offers both the application services, letting the buyer decide which one they prefer to pick, subject to their functionality and need.

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The good news is that DexLab offers both Hadoop and Apache Spark Certification Training. What’s more, a recent admission drive is ongoing #BigDataIngestion. Enroll now and enjoy 10% discount on big data certification training courses.

The blog originally was published on – www.forbes.com/sites/bernardmarr/2015/06/22/spark-or-hadoop-which-is-the-best-big-data-framework/2/#714061d161d6

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Hierarchical Clustering: Foundational Concepts and Example of Agglomerative Clustering

Posted on June 22, 2018June 22, 2018 by Dexlab

Hierarchical Clustering: Foundational Concepts and Example of Agglomerative Clustering

Clustering is the process of organizing objects into groups called clusters. The members of a cluster are ‘’similar’’ between them and ‘’dissimilar’’ to members of other groups.

In the previous blog, we have discussed basic concepts of clustering and given an overview of the various methods of clustering. In this blog, we will take up Hierarchical Clustering in greater details.

Hierarchical Clustering:

Hierarchical Clustering is a method of cluster analysis that develops a hierarchy (ladder) of clusters. The two main techniques used for hierarchical clustering are Agglomerative and Divisive.

Agglomerative Clustering:

In the beginning of the analysis, each data point is treated as a singleton cluster. Then, clusters are combined until all points have been merged into a single remaining cluster. This method of clustering wherein a ‘’bottom up’’ approach is followed and clusters are merged as one moves up the hierarchy is called Agglomerative clustering.

Linkage types:

The clustering is done with the help of linkage types. A particular linkage type is used to get the distance between points and then assign it to various clusters. There are three linkage types used in Hierarchical clustering- single linkage, complete linkage and average linkage.

Single linkage hierarchical clustering: In this linkage type, two clusters whose two closest members have the shortest distance (or two clusters with the smallest minimum pairwise distance) are merged in each step.

Complete linkage hierarchical clustering: In this type, two clusters whose merger has the smallest diameter (two clusters having the smallest maximum pairwise distance) are merged in each step.

Average linkage hierarchical clustering: In this type, two clusters whose merger has the smallest average distance between data points (or two clusters with the smallest average pairwise distance), are merged in each step.

Single linkage looks at the minimum distance between points, complete linkage looks at the maximum distance between points while average linkage looks at the average distance between points.

Now, let’s look at an example of Agglomerative clustering.

The first step in clustering is computing the distance between every pair of data points that we want to cluster. So, we form a distance matrix. It should be noted that a distance matrix is symmetrical (distance between x and y is the same as the distance between y and x) and has zeros in its diagonal (every point is at a distance zero from itself). The table below shows a distance matrix- only lower triangle is shown an as the upper one can be filled with reflection.

Next, we begin clustering. The smallest distance is between 3 and 5 and they get merged first into the cluster ‘35’.

After this, we replace the entries 3 and 5 by ‘35’ and form a new distance matrix. Here, we are employing complete linkage clustering. The distance between ‘35’ and a data point is the maximum of the distance between the specific data point and 3 or the specific data point and 5. This is followed for every data point. For example, D(1,3)=3 and D(1,5) =11, so as per complete linkage clustering rules we take D(1,’35’)=11. The new distance matrix is shown below.

Again, the items with the smallest distance get clustered. This will be 2 and 4. Following this process for 6 steps, everything gets clustered. This has been summarized in the diagram below. In this plot, y axis represents the distance between data points at the time of clustering and this is known as cluster height.

Complete Linkage

If single linkage clustering was used for the same distance matrix, then we would get a single linkage dendogram as shown below. Here, we start with cluster ‘35’. But the distance between ‘35’ and each data point is the minimum of D(x,3) and D(x,5). Therefore, D(1,’35’)=3.

Single Linkage

Agglomerative hierarchical clustering finds many applications in marketing. It is used to group customers together on the basis of product preference and liking. It effectively determines variations in consumer preferences and helps improving marketing strategies.

In the next blog, we will explain Divisive clustering and other important methods of clustering, like Ward’s Method. So, stay tuned and follow Dexlab Analytics. We are a leading big data Hadoop training institute in Gurgaon. Enroll for our expert-guided certification courses on big data Hadoop and avail flat 10% discount!

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Check back for the blog – A Comprehensive Guide on Clustering and Its Different Methods

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