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 are the advantages of CMOS logic, What are the advantages of CMOS logi...

What are the advantages of CMOS logic Ans: Advantages of CMOS Logic: (i) The power dissipation is mini-mum of all the logic families (ii) LSI and VLSI are possible

Define digital computers system, Q. Define Digital computers system? Di...

Q. Define Digital computers system? Digital computers, in general, are automatic machines that accept data and instructions, perform predefined operations very quickly on the d

Explain short note about molap?, Classic form of OLAP is called as MOLAP an...

Classic form of OLAP is called as MOLAP and it is often known as OLAP. Simple database structures like time period, product, location, etc are used. Functioning of each and every d

Sequential execution of instructions in risc, Q. Sequential Execution of In...

Q. Sequential Execution of Instructions in RISC? Let's describe pipelining in RISC with an illustration program execution sample. Take the given program (R denotes register).

Eight-stage process - conjunctive normal forms, Eight-stage process - Conju...

Eight-stage process - Conjunctive normal forms: Hence we notice the following eight-stage process converts any sentence with CNF as:  1.  Eliminate all arrow connectives by

Detail explanation of cryptographic modules, Detail explanation of Cryptogr...

Detail explanation of Cryptographic modules Physical security of the cryptographic modules is also built in order to provide total security of the whole system and protect from

Static memories - computer architecture, Static memories Circuits c...

Static memories Circuits capable of receiving their state as long as power is applied volatile Static RAM(SRAM)

What is a unix device driver, A UNIX device driver is ? Ans. A UNIX devi...

A UNIX device driver is ? Ans. A UNIX device driver is structured in two halves termed as top half and bottom half.

What do you mean by e-brokerage, What do you mean by e-brokerage? E-bro...

What do you mean by e-brokerage? E-brokerage is an investment house which permits you to buy and sell stocks and acquire investment information through its Web site. E-comme

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