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 feram?, Ferroelectric RAM is a random-access memory same in constr...

Ferroelectric RAM is a random-access memory same in construction to DRAM but uses a ferroelectric layer rather of a dielectric layer to achieve non-volatility. FeRAM is one of a gr

What are difference between latches and flipflops, What are difference betw...

What are difference between latches and flipflops? Difference : Latches are level-sensitive, while, flipflops is edge sensitive. It means to say edge sensitive that O/p change

Make a generalized program that accepts a number and base, Q. Make a gener...

Q. Make a generalized program that accepts a number & base, convert it into the given base. Perform necessary validations.

Explain importance of modems used in data transfer, Explain importance of ...

Explain importance of modems used in data transfer and list some of the V-series recommendations. The series also describes a variety of DCEs using different type modulatio

Define hex directive, Q. Define HEX directive? HEX: HEX directive enabl...

Q. Define HEX directive? HEX: HEX directive enables the coding of hexadecimal values in body of the program. That statement directs assembler to treat tokens in source file wh

Difference between blocking and non-blocking, Difference between blocking a...

Difference between blocking and non-blocking Verilog  language  has  two  forms  of  the  procedural  assignment  statement:  blocking  and  nonblocking. The two are distinguis

Steps uesd in quine mckluskey method, Q. Steps uesd in quine mckluskey meth...

Q. Steps uesd in quine mckluskey method? Step I: Build a table in that every term of expression is represented in row (Expression must be in SOP form). Terms can be expres

Define a structure, Define a structure. A structure having an ordered g...

Define a structure. A structure having an ordered group of data objects. Unlike the elements of an array, the data objects within a structure can have varied data types. Every

Explain a TTL NAND gate and its operation, Give the circuit of a TTL NAND g...

Give the circuit of a TTL NAND gate and explain its operation in brief. Ans: Operation of TTL NAND Gate: Fig.(d) Demonstrates a TTL NAND gate with a totem pole output.

What are the "field" and "chain" statements, What are the "field" and "chai...

What are the "field" and "chain" Statements? The FIELD and CHAIN flow logic statements let you Program your own checks. FIELD and CHAIN tell the system which fields you are ch

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