文档介绍：Rough Sets
Lin Shang
Dept. puter Science and Technology
******@nju.
./shanglin/
Dept. puter Science and Technology, Nanjing University
What can Rough Set do?
• for toy data…
• in real world…
Dept. puter Science and Technology, Nanjing University
for toy data…
patients Attributes Decision Attribute
Condition Attribute
Patient Headache Muscle-pain Temperature Flu
p1 yes yes normal no
p2 yes yes high yes
p3 yes yes very high yes
p4 no yes normal no
p5 no no high no
p6 no yes very high yes
IS(Information System)
Dept. puter Science and Technology, Nanjing University
Problem?
Patient Headache Muscle-pain Temperature Flu
p1 yes yes normal no
p2 yes yes high yes
p3 yes yes very high yes
p4 no yes normal no
p5 no no high no
p6 no yes very high yes
1. Reduction
2. Rule generation
3. Attribute depencency or Significance of Attributes
4. …
Dept. puter Science and Technology, Nanjing University
1. Reduction
Patient Headache Muscle-pain Temperature Flu
p1 yes yes normal no
p2 yes yes high yes
p3 yes yes very high yes
p4 no yes normal no
p5 no no high no
p6 no yes very high yes
patient flu
headache muscle-pain temperature ? (less)
temperature muscle-pain
Dept. puter Science and Technology, Nanjing University
rudiments
Patient Headache Muscle-pain Temperature Flu
p1 yes yes normal no
p2 yes yes high yes
p3 yes yes very high yes
p4 no yes normal no
p5 no no high no
p6 no yes very high yes
B={Headache, Muscle-pain} U/B={{p1, p2 , p3 }, { p4, p6} ,{p5}}={B1,B2,B3}
X={p2,p3,p5}
BX== B3{5} p
BX=∪= B1 B 3 {1,2,3,5} p p p p
Dept. puter Science and Technology, Nanjing University
rudiments
Patient Headache Muscle-pain Temperature Flu
p1 yes yes normal no
p2 yes yes high yes
p3 yes yes very high yes
p4 no yes normal no
p5 no no high no
p6 no yes very high yes
Definitions:
dispensable Reducts: {Headache, Temperature}
Independent
reduct or {Muscle-pain, Te