ﻢِ ﺴﺑِ ا ﻦِﻤﺣﺮﻟا ﻪﻠﻟا ِﻢِ · Make a Schedule of 24 Hours to get...
Transcript of ﻢِ ﺴﺑِ ا ﻦِﻤﺣﺮﻟا ﻪﻠﻟا ِﻢِ · Make a Schedule of 24 Hours to get...
ن احم حيم بسم الله الر لر
Machine LearningLecture 10 – Instance Based Learning
Dr. Rao Muhammad Adeel Nawab
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How to Work?
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تعين ا س���﮳�ه
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﮴م � ﮵ا ال�ه �ہ . ن
�ں﮵ ے �ہ﮴�﮲�� �ے �د د ما ی �﮳ھ �ہ
اور �﮴
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ی﮴��ں﮵ ہہاری
﮲ت﮴ ���﮳ی �
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﯀� و ��و
﮴وں � �ں﮵ �ہ .دعائ
�ط : دعا تقيم صر �ط ٱٱلمس� مٱٱهد� ٱٱلصر �ن ٱ�نعمت �ليه ٱٱ����﮳�ه
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﮴��ں﮵ ��د﮵�ی راه د�ھا ان �و�وں �ی راه �﮳ں﮲ ��﮷ � ﮵ا�ہ . ب
Power of Effort & Dua
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�هم� خر لي وا�تر لي الل�متنا لا� ما �ل
�ب�انك لا �لم لنا ا س�
�ك ٱ�نت العليم الحكيم ن�ا
ح لي صدري رب اشر لي امري و�سر
وا�لل عقدة من لساني یفقهوا قولي
Dua – Take Help from Allah Before Starting Any Task
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Mainly get Excellence in two things
Course Focus
Become a great Human Being
Become a great Machine Learning Engineer
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Introduction to Instance-based LearningNearest Neighbor ClassificationDistance Measures
ReadingChapter 8 of MitchellChapter 5 ”Memory-based Learning Algorithms” in W. Daelemans, J. Zavrel, K. van der
Lecture Outline
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Balanced Life is Ideal Life
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Make a Schedule
BEGINNER INTERMEDIATE EXPERT EXCELLENCE
Make a Schedule of 24 Hours to get EXCELLENCE in 5 thingsA Journey from
You must have a combination of five things with different variations. However, aggregate will be same.
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Second - Spirituality
ذا�ہ �� غغ کا ذ�� روح ےالله
Read Quran-e-Pak dailyRead Durood Sharif / Istighfar / any other Zikar at least 300 times dailyOffer 5 prayers daily
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Second – Spirituality (Cont.)
Excellence in Spiritualityھ ا�ت ے ہہ �ی � ےدغا �ے �ی � ھا وا�ٹ کام �ہ و
تگا� ے
ا� جج
Introduction to Instance-based Learning
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The machine learning algorithms we have examined so far
FIND-S algorithm
Candidate Elimination algorithm
Decision Tree Learning algorithm (ID3)
Artificial Neural Networks
Deep Learning algorithms
Bayesian Learning algorithm (Naïve Bayes)
Instance-based Learning - Introduction
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Constructan explicit representation of the target function(approximated target function)from a
Set of training examplesSet of hypotheses
approximated target function is applied, and thetarget classification returned
Instance-based Learning - Introduction
To classify a new (or unseen) instance
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Instance-based Learning – Introduction (cont…)
In contrast, instance-based algorithms
simply store the training examples
To classify a new (or unseen) instance
It is compared to the stored examples
Depending on its relationship to training examples
It is assigned a target classification
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Lazy Methods vs Eager Methods
Because instance-based methods defer processing until a new instance must be classified, they are called lazy methods
Lazy Methods
Methods which build representations of the target function as training examples are presented are called eager methods
Eager Methods
Nearest Neighbor Classification
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k-Nearest Neighbor Learning
Instances Representation
Generally, assumes instances are represented as n-tuples of real-values, i.e. as points in n-dimensional space
Distance between Instances
Distance between any two instances is defined in terms of theEuclidean distance
k-NN is the “grand-daddy” of instance-based methods
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Instance-Based Classifiers
Atr 1 … … … Atr N ClasssABBCACB
Atr 1 … … … Atr N
Set of Stored Cases
Unseen Cases
Store the training records.Use training records topredict the class label ofunseen cases.
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If there is long hair like a female, covered head with scarflike a female, then it’s probably a female
Nearest Neighbor Classifiers
Training Record
Test Record
Basic idea
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If there is long hair like a female, covered head with scarflike a female, then it’s probably a female
Nearest Neighbor Classifiers
Basic idea
Training Record
Test Record
Compute Distance
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If there is long hair like a female, covered head with scarflike a female, then it’s probably a female
Nearest Neighbor Classifiers
Basic idea
Training Record
Test Record
Compute Distance
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Nearest Neighbor Classifiers
Unknown record
The set of stored recordsDistance Metric to compute distance between recordsThe value of k, the number of nearest neighbors to retrieve
1
2
3
Requires three things
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Nearest Neighbor Classifiers (cont…)
Unknown record
Compute distance to other training recordsIdentify k nearest neighbors Use class labels of nearest neighbors to determine the class label of unknown record (e.g., by taking majority vote)
To classify an unknown record
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K-nearest neighbors of a record x are data points that have the k smallest distance to x
Definition of Nearest Neighbor
X X X
(a) 1-nearest neighbor (b) 2-nearest neighbor (c) 3-nearest neighbor
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Nearest Neighbor Classification
𝒅𝒅(𝒑𝒑,𝒒𝒒) = �𝒊𝒊
(𝒑𝒑𝒊𝒊 − 𝒒𝒒𝒊𝒊)𝟐𝟐
Compute distance between two points
Euclidean distance
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Nearest Neighbor Classification (cont...)
Determine the class from nearest neighbor list
Take the majority vote of class labels among the k-nearest neighbors
Weigh the vote according to distance
weight factor, w = 1 / d2
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Nearest Neighbor Classification
If k is too small, sensitive to noise pointsIf k is too large, neighborhood may include points from other classes
X
Choosing the value of K
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Nearest Neighbor Classification
Height of a person may vary from 1.5m to 1.8mWeight of a person may vary from 90lb to 300lbIncome of a person may vary from $10K to $1M
Example
Attributes may have to be scaled to prevent distance measures from being dominated by one of the attributes
Scaling issues
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Nearest Neighbor Classification
k-NN classifiers are lazy learners
It does not build models explicitly
Unlike eager learners such as decision tree induction and rule-based systems
Classifying unknown records are relativelyexpensive
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Nearest Neighbor Classification
Problem with Euclidean measure
Can produce counter-intuitive results
High dimensional data curse of dimensionality
Distance Measures
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Choosing the correct distance function is essentialEucledian, MinkowskiSimple Matching CoefficientJaccard measureCosine Measure
Distance Measures
Distance measure for strings
Edit distance
Example
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Distance between two strings: minimal number of operations to transform one into another
Insert a characterDelete a characterReplace a character with another
Edit Distance
Hello Jello distance = 1
Good Goodbye distance = 3
Example