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2008-10-27 15:59 |
Matlab中超几何分布作图介绍
在用Matlab绘制各种常用概率分布的密度函数时，都比较简单，唯独超几何分布试了几次都不成功，输出结果总是 }H^^v[4
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查看了一下帮助 help hygepdf 1k({(\>qq
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HYGEPDF Hypergeometric probability density function. LA0x6E+I
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Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability &< b7T $c
density function at X with integer parameters M, K, and N. $^ 3 f}IzA
Note: The density function is zero unless X is an integer. `t 2! M\)
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The size of Y is the common size of the input arguments. A scalar input >p:fWQ6
functions as a constant matrix of the same size as the other inputs. +:Zi(SuS]
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See also hygecdf, hygeinv, hygernd, hygestat, pdf. 'FXZ`+r|
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Reference page in Help browser 4(ZV\}j1
doc hygepdf ir?9{t/()
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超几何分布参数较多，这里关于三个参数的指代不详。又在互联网上查了相关资料，包括该函数的定义式： [AwE
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http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m C" WZsF^3
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直到发现这个例子后才清楚各个参数所代表的具体意义。 xn[di-L F
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Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random? c5pG?jr+d
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p = hygepdf(0:5,100,20,10) iDJ2dM} v
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p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215 Qg=~n:j
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详细可参见： 9b6h!(
http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 hI 0l2OE
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果然与一般对超几何分布公式字母惯常表示方式有所不同。尝试将上述分布作图如下 I^=M>_ s4
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x = 0:5 ~ .-'pdz%
p = hygepdf(x,100,20,10); Gx($q;8
plot(x,p,':k*')
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