Showing posts with label Machine Learning. Show all posts
Showing posts with label Machine Learning. Show all posts

Components of AI

AI is a vast field for research and it has got applications in almost all possible domain. By keeping this in mind, research in AI has focussed mainly on the following components of AI:
  1. Learning
  2. Reasoning
  3. Problem Solving
  4. Perception
  5. Knowledge representation
  6. Language understanding.
1. Learning
        Learning is a very essential part of AI and it happens in a number of different forms. The simplest form of learning is by trial and error. In this form, the program remembers the section that has given the desired output and discards the other trial actions and learns by itself. For example, in chess (program) mate-in-one chess problems might try out moves at random until one is found that achieves mate. Here the program remembers the successful move and next time the computer is given the same problem it is able to produce the result instantly. It is also called unsupervised learning. The simple learning of individual items - solutions to problems, worlds of vocabulary, etc. is known as rote learning. In the case of rote learning, the program simply remembers the problem solution pairs or individual items. In other cases, a solution to few of the problems is given as input to the system, the basis on which the system or program needs to generate solutions for new problems. This is known as supervised learning.

2. Reasoning
        Reasoning is also called as logic or generating judgments from the given set of facts. The reasoning is carried out based on a strict rule of validity to perform a specified task. Reasoning can be of two types, deductive or inductive. The deductive reasoning is in which the truth of the premised guarantees the truth of the conclusion while, in case of inductive reasoning, the truth of the premises supports the conclusion but it cannot be fully dependent on the premises. In programming logic generally, deductive inferences are used. Reasoning involves drawing inferences that are relevant to the given problem or situation.

3. Problem Solving
        AI addresses a huge variety of problems. For example, finding out winning moves on the board games, planning actions in order to achieve the defined task, identifying various objects from given images, etc. Problem-solving methods are mainly divided into two types special-purpose and general-purpose methods. General purpose methods are applicable to a wide range of problems one used in AI is means-end analysis, which involves the step-by-step reduction of the difference between the current state and the goal state. Special purpose methods are customized to solve a particular type of problems.

4. Perception
        In order to work in the environment, intelligent agents need to scan the environment and the various objects in it by means of different sense-organs, real or artificial. Agent scans the environment using sense organs like camera, temperature sensor, etc. This is called perception. After capturing various scenes, perceiver analyses the different objects in it and extracts their features and relationships among them.

5. Knowledge representation
        The information obtained from the environment through sensors may not be in the format required by the system. Hence, it needs to be represented in standard formats for further processing like learning various patterns, deducing inference, comparing with past objects, etc. There are various knowledge representation techniques like Prepositional logic and First-order logic.

6. Language understanding
        Natural Language Processing, involves machines or robots to understand and process the language that human speaks, and infer knowledge from the speech input. It also involves the active participation from a machine in the form of dialog i.e. NLP aims at the text or verbal output from the machine or robot. The input and output of an NLP system can be speech and written text respectively.

Write short note on Decision Tree based Classification Approach

  • Training dataset should be class-labeled for learning of decision trees in decision tree induction.
  • A decision tree represents rules and it is very a popular tool for classification and prediction.
  • Rules are easy to understand and can be directly used in SQL to retrieve the records from the database.
  • To recognize and approve the discovered knowledge acquired from decision model is a crucial task.
  • There are many algorithms to build decision tree:
    • ID3 (Iterative Dichotomiser)
    • C4.5 (Successor of ID3)
    • CART (Classification and Regression Tree)
    • CHAID (Chi-square Automatic Interaction Detector)
Decision Tree representation
  • A decision tree classifier has a tree type structure which has leaf-nodes and decision nodes.
  • A leaf node is that last node of each branch and indicates the class label or value of a target attribute.
  • A decision node is the node of a tree which has leaf node or sub-tree. Some test to be carried on each value of decision node to get the decision of class label or to get next sub-tree.
Decision Tree represents for play tennis

What are the key tasks of Machine Learning?

Machine Learning is gaining some useful information from the data. Usually, Machine Learning is of two types Supervised Learning and Unsupervised Learning.

Supervised Learning
    Classification and Regression are examples of Machine Learning. The task of classification is to predict what class an instance of data should fall into. Another task in machine learning is a regression which predicts a numeric value.  Classification deals with predicting discrete value like True/False, Male/Female, 1/2/3 Regression is used when the class to predict is of continuous value say from 0 to 100, -inf to +inf. The best example of regression is a best-fit line drawn through some data points to generalize the data points. This set of problems is called as supervised learning because here we tell the algorithm what to predict i.e. we know the label or target value.

Unsupervised Learning
    In unsupervised learning, there's no label or target value given for the data. A task where similar items grouped together to form a cluster is known as clustering. Another task of unsupervised learning may be reducing the data from many features to a small number so that it becomes easier to visualize it in two or three dimensions.

The following table lists some common tasks in machine learning with algorithms used to solve these tasks.

Supervise Learning tasks
k-Nearest Neighbors Linear
Naive Bayes Locally weighted linear
Support Vector Machines Ridge
Decision Trees Lasso
Unsupervised Learning tasks
k-means Expectation minimization
DBSCAN Parzen window