第6章 不确定性推理部分参考
答案
八年级地理上册填图题岩土工程勘察试题省略号的作用及举例应急救援安全知识车间5s试题及答案
6.8 设有如下一组推理规则:
r1: IF E1 THEN E2 (0.6)
r2: IF E2 AND E3 THEN E4 (0.7)
r3: IF E4 THEN H (0.8)
r4: IF E5 THEN H (0.9)
且已知CF(E1)=0.5, CF(E3)=0.6, CF(E5)=0.7。求CF(H)=?
解:(1) 先由r1求CF(E2)
CF(E2)=0.6 × max{0,CF(E1)}
=0.6 × max{0,0.5}=0.3
(2) 再由r2求CF(E4)
CF(E4)=0.7 × max{0, min{CF(E2 ), CF(E3 )}}
=0.7 × max{0, min{0.3, 0.6}}=0.21
(3) 再由r3求CF1(H)
CF1(H)= 0.8 × max{0,CF(E4)}
=0.8 × max{0, 0.21)}=0.168
(4) 再由r4求CF2(H)
CF2(H)= 0.9 ×max{0,CF(E5)}
=0.9 ×max{0, 0.7)}=0.63
(5) 最后对CF1(H )和CF2(H)进行合成,求出CF(H)
CF(H)= CF1(H)+CF2(H)+ CF1(H) × CF2(H)
=0.692
6.10 设有如下推理规则
r1: IF E1 THEN (2, 0.00001) H1
r2: IF E2 THEN (100, 0.0001) H1
r3: IF E3 THEN (200, 0.001) H2
r4: IF H1 THEN (50, 0.1) H2
且已知P(E1)= P(E2)= P(H3)=0.6, P(H1)=0.091, P(H2)=0.01, 又由用户告知:
P(E1| S1)=0.84, P(E2|S2)=0.68, P(E3|S3)=0.36
请用主观Bayes方法求P(H2|S1, S2, S3)=?
解:(1) 由r1计算O(H1| S1)
先把H1的先验概率更新为在E1下的后验概率P(H1| E1)
P(H1| E1)=(LS1 × P(H1)) / ((LS1-1) × P(H1)+1)
=(2 × 0.091) / ((2 -1) × 0.091 +1)
=0.16682
由于P(E1|S1)=0.84 > P(E1),使用P(H | S)公式的后半部分,得到在当前观察S1下的后验概率P(H1| S1)和后验几率O(H1| S1)
P(H1| S1) = P(H1) + ((P(H1| E1) – P(H1)) / (1 - P(E1))) × (P(E1| S1) – P(E1))
= 0.091 + (0.16682 –0.091) / (1 – 0.6)) × (0.84 – 0.6)
=0.091 + 0.18955 × 0.24 = 0.136492
O(H1| S1) = P(H1| S1) / (1 - P(H1| S1))
= 0.15807
(2) 由r2计算O(H1| S2)
先把H1的先验概率更新为在E2下的后验概率P(H1| E2)
P(H1| E2)=(LS2 × P(H1)) / ((LS2-1) × P(H1)+1)
=(100 × 0.091) / ((100 -1) × 0.091 +1)
=0.90918
由于P(E2|S2)=0.68 > P(E2),使用P(H | S)公式的后半部分,得到在当前观察S2下的后验概率P(H1| S2)和后验几率O(H1| S2)
P(H1| S2) = P(H1) + ((P(H1| E2) – P(H1)) / (1 - P(E2))) × (P(E2| S2) – P(E2))
= 0.091 + (0.90918 –0.091) / (1 – 0.6)) × (0.68 – 0.6)
=0.25464
O(H1| S2) = P(H1| S2) / (1 - P(H1| S2))
=0.34163
(3) 计算O(H1| S1,S2)和P(H1| S1,S2)
先将H1的先验概率转换为先验几率
O(H1) = P(H1) / (1 - P(H1)) = 0.091/(1-0.091)=0.10011
再根据合成公式计算H1的后验几率
O(H1| S1,S2)= (O(H1| S1) / O(H1)) × (O(H1| S2) / O(H1)) × O(H1)
= (0.15807 / 0.10011) × (0.34163) / 0.10011) × 0.10011
= 0.53942
再将该后验几率转换为后验概率
P(H1| S1,S2) = O(H1| S1,S2) / (1+ O(H1| S1,S2))
= 0.35040
(4) 由r3计算O(H2| S3)
先把H2的先验概率更新为在E3下的后验概率P(H2| E3)
P(H2| E3)=(LS3 × P(H2)) / ((LS3-1) × P(H2)+1)
=(200 × 0.01) / ((200 -1) × 0.01 +1)
=0.09569
由于P(E3|S3)=0.36 < P(E3),使用P(H | S)公式的前半部分,得到在当前观察S3下的后验概率P(H2| S3)和后验几率O(H2| S3)
P(H2| S3) = P(H2 | ¬ E3) + (P(H2) – P(H2| ¬E3)) / P(E3)) × P(E3| S3)
由当E3肯定不存在时有
P(H2 | ¬ E3) = LN3 × P(H2) / ((LN3-1) × P(H2) +1)
= 0.001 × 0.01 / ((0.001 - 1) × 0.01 + 1)
= 0.00001
因此有
P(H2| S3) = P(H2 | ¬ E3) + (P(H2) – P(H2| ¬E3)) / P(E3)) × P(E3| S3)
=0.00001+((0.01-0.00001) / 0.6) × 0.36
=0.00600
O(H2| S3) = P(H2| S3) / (1 - P(H2| S3))
=0.00604
(5) 由r4计算O(H2| H1)
先把H2的先验概率更新为在H1下的后验概率P(H2| H1)
P(H2| H1)=(LS4 × P(H2)) / ((LS4-1) × P(H2)+1)
=(50 × 0.01) / ((50 -1) × 0.01 +1)
=0.33557
由于P(H1| S1,S2)=0.35040 > P(H1),使用P(H | S)公式的后半部分,得到在当前观察S1,S2下H2的后验概率P(H2| S1,S2)和后验几率O(H2| S1,S2)
P(H2| S1,S2) = P(H2) + ((P(H2| H1) – P(H2)) / (1 - P(H1))) × (P(H1| S1,S2) – P(H1))
= 0.01 + (0.33557 –0.01) / (1 – 0.091)) × (0.35040 – 0.091)
=0.10291
O(H2| S1,S2) = P(H2| S1, S2) / (1 - P(H2| S1, S2))
=0.10291/ (1 - 0.10291) = 0.11472
(6) 计算O(H2| S1,S2,S3)和P(H2| S1,S2,S3)
先将H2的先验概率转换为先验几率
O(H2) = P(H2) / (1 - P(H2) )= 0.01 / (1-0.01)=0.01010
再根据合成公式计算H1的后验几率
O(H2| S1,S2,S3)= (O(H2| S1,S2) / O(H2)) × (O(H2| S3) / O(H2)) ×O(H2)
= (0.11472 / 0.01010) × (0.00604) / 0.01010) × 0.01010
=0.06832
再将该后验几率转换为后验概率
P(H2| S1,S2,S3) = O(H1| S1,S2,S3) / (1+ O(H1| S1,S2,S3))
= 0.06832 / (1+ 0.06832) = 0.06395
可见,H2原来的概率是0.01,经过上述推理后得到的后验概率是0.06395,它相当于先验概率的6倍多。
6.11设有如下推理规则
r1: IF E1 THEN (100, 0.1) H1
r2: IF E2 THEN (50, 0.5) H2
r3: IF E3 THEN (5, 0.05) H3
且已知P(H1)=0.02, P(H2)=0.2, P(H3)=0.4,请计算当证据E1,E2,E3存在或不存在时P(Hi | Ei)或P(Hi |﹁Ei)的值各是多少(i=1, 2, 3)?
解:(1) 当E1、E2、E3肯定存在时,根据r1、r2、r3有
P(H1 | E1) = (LS1 × P(H1)) / ((LS1-1) × P(H1)+1)
= (100 × 0.02) / ((100 -1) × 0.02 +1)
=0.671
P(H2 | E2) = (LS2 × P(H2)) / ((LS2-1) × P(H2)+1)
= (50 × 0.2) / ((50 -1) × 0.2 +1)
=0.9921
P(H3 | E3) = (LS3 × P(H3)) / ((LS3-1) × P(H3)+1)
= (5 × 0.4) / ((5 -1) × 0.4 +1)
=0.769
(2) 当E1、E2、E3肯定存在时,根据r1、r2、r3有
P(H1 | ¬E1) = (LN1 × P(H1)) / ((LN1-1) × P(H1)+1)
= (0.1 × 0.02) / ((0.1 -1) × 0.02 +1)
=0.002
P(H2 | ¬E2) = (LN2 × P(H2)) / ((LN2-1) × P(H2)+1)
= (0.5 × 0.2) / ((0.5 -1) × 0.2 +1)
=0.111
P(H3 | ¬E3) = (LN3 × P(H3)) / ((LN3-1) × P(H3)+1)
= (0.05 × 0.4) / ((0.05 -1) × 0.4 +1)
=0.032
6.13 设有如下一组推理规则:
r1: IF E1 AND E2 THEN A={a} (CF={0.9})
r2: IF E2 AND (E3 OR E4) THEN B={b1, b2} (CF={0.8, 0.7})
r3: IF A THEN H={h1, h2, h3} (CF={0.6, 0.5, 0.4})
r4: IF B THEN H={h1, h2, h3} (CF={0.3, 0.2, 0.1})
且已知初始证据的确定性分别为:
CER(E1)=0.6, CER(E2)=0.7, CER(E3)=0.8, CER(E4)=0.9。
假设|Ω|=10,求CER(H)。
解:其推理过程参考例6.9
具体过程略
6.15 设
U=V={1,2,3,4}
且有如下推理规则:
IF x is 少 THEN y is 多
其中,“少”与“多”分别是U与V上的模糊集,设
少=0.9/1+0.7/2+0.4/3
多=0.3/2+0.7/3+0.9/4
已知事实为
x is 较少
“较少”的模糊集为
较少=0.8/1+0.5/2+0.2/3
请用模糊关系Rm求出模糊结论。
解:先用模糊关系Rm求出规则
IF x is 少 THEN y is 多
所包含的模糊关系Rm
Rm (1,1)=(0.9∧0)∨(1-0.9)=0.1
Rm (1,2)=(0.9∧0.3)∨(1-0.9)=0.3
Rm (1,3)=(0.9∧0.7)∨(1-0.9)=0.7
Rm (1,4)=(0.9∧0.9)∨(1-0.9)=0.7
Rm (2,1)=(0.7∧0)∨(1-0.7)=0.3
Rm (2,2)=(0.7∧0.3)∨(1-0.7)=0.3
Rm (2,3)=(0.7∧0.7)∨(1-0.7)=0.7
Rm (2,4)=(0.7∧0.9)∨(1-0.7)=0.7
Rm (3,1)=(0.4∧0)∨(1-0.4)=0.6
Rm (3,2)=(0.4∧0.3)∨(1-0.4)=0.6
Rm (3,3)=(0.4∧0.7)∨(1-0.4)=0.6
Rm (3,4)=(0.4∧0.9)∨(1-0.4)=0.6
Rm (4,1)=(0∧0)∨(1-0)=1
Rm (4,2)=(0∧0.3)∨(1-0)=1
Rm (4,3)=(0∧0.7)∨(1-0)=1
Rm (3,4)=(0∧0.9)∨(1-0)=1
即:
因此有
即,模糊结论为
Y’={0.3, 0.3, 0.7, 0.8}
6.16 设
U=V=W={1,2,3,4}
且设有如下规则:
r1:IF x is F THEN y is G
r2:IF y is G THEN z is H
r3:IF x is F THEN z is H
其中,F、G、H的模糊集分别为:
F=1/1+0.8/2+0.5/3+0.4/4
G=0.1/2+0.2/3+0.4/4
H=0.2/2+0.5/3+0.8/4
请分别对各种模糊关系验证满足模糊三段论的情况。
解:本
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的解题思路是:
由模糊集F和G求出r1所
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示的模糊关系R1m, R1c, R1g
再由模糊集G和H求出r2所表示的模糊关系R2m, R2c, R2g
再由模糊集F和H求出r3所表示的模糊关系R3m, R3c, R3g
然后再将R1m, R1c, R1g分别与R2m, R2c, R2g合成得R12 m, R12c, R12g
最后将R12 m, R12c, R12g分别与R3m, R3c, R3g比较
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