Arbitrary categorisation - learning decision trees, Computer Engineering

Assignment Help:

Arbitrary categorisation - learning decision trees:

Through visualising  a set of boxes with some balls in. There if all the balls were in a single box so this would be nicely ordered but it would be extremely easy to find a particular ball. Moreover If the balls were distributed amongst the boxes then this would not be so nicely ordered but it might take rather a whereas to find a particular ball. It means if we were going to define a measure based at this notion of purity then we would want to be able to calculate a value for each box based on the number of balls in it so then take the sum of these as the overall measure. Thus we would want to reward two situations: nearly empty boxes as very neat and boxes just with nearly all the balls in as also very neat. However this is the basis for the general entropy measure that is defined follows like: 

Now next here instantly an arbitrary categorisation like C into categories c1, ..., cn and a set of examples, S, for that the proportion of examples in ci is pi, then the entropy of S is as: 

198_Arbitrary categorisation - learning decision trees.png

Here measure satisfies our criteria that is of the -p*log2(p) construction: where p gets close to zero that is the category has only a few examples in it so then the  log(p) becomes a big negative number and the  p  part dominates the calculation then the entropy works out to be nearly zero. However make it sure that entropy calculates the disorder in the data in this low score is good and as it reflects our desire to reward categories with few examples in. Such of similarly if p gets close to 1 then that's the category has most of the examples in so then the  log(p) part gets very close to zero but it  is this that dominates the calculation thus the overall value gets close to zero. Thus we see that both where the category is nearly  -  or completely  -  empty and when the category nearly contains as - or completely contains as  - all the examples and the score for the category gets close to zero that models what we wanted it to. But note that 0*ln(0) is taken to be zero by convention them.


Related Discussions:- Arbitrary categorisation - learning decision trees

What is meant by hotspots, What is meant by hotspots? A Hotspot is a l...

What is meant by hotspots? A Hotspot is a list area where the mouse pointer appears as an upright hand symbol. When a user points to that area (and the hand cursor is active),

Mobile computing, Explain the key characteristics of mobile computing appli...

Explain the key characteristics of mobile computing applications

How to insert script in dreamweaver, Q. How to insert script in dreamweaver...

Q. How to insert script in dreamweaver? Step 1: Click on Insert Step 2: Click on Script Step 3: Choose the type of Script Step 4: Write the code in "Content" Step 5: T

Explain syntax of recursion, Syntax of recursion int fib(int num) /*...

Syntax of recursion int fib(int num) /* Fibonacci value of a number */ {      switch(num) { case 0: return(0); break; case 1: return(1); break; default:  /* Incl

What is a spool request, What is a Spool request? Spool requests are f...

What is a Spool request? Spool requests are formed during dialog or background processing and placed in the spool database with information about the printer and print format.

Explain the matlab language, This is a high-level matrix/array language wit...

This is a high-level matrix/array language with control flow statements, functions, data structures, input/output, and object-oriented programming features. It permits both "progra

What are the risks involved in electronic payment systems, What are the ris...

What are the risks involved in Electronic Payment Systems?    From the customer's perspective: Dishonest merchants or financial service providers Stolen payment

Describe about javascript, World Wide Web (WWW) began as a text-only medium...

World Wide Web (WWW) began as a text-only medium. First version doesn't even have the capability to include graphics on a page. Today's Web sites include sound animation, graphics,

Using the editor or debugger, Write a script that will read from a file x a...

Write a script that will read from a file x and y data points in the following format: x   0    y  1 x  1.3  y  2.2 x  2.2  y  6 x  3.4  y  7.4 The format of each line in the

Perceptrons of artificial neural networks, Perceptrons: However the we...

Perceptrons: However the weights in any ANN are usually just real numbers and the learning problem boils down to choosing the best value for each weight in the network. Becaus

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd