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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 ZF|+W?0&%
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ans = 'u_t< F ]b
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查看了一下帮助 help hygepdf !{ )tSipd
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HYGEPDF Hypergeometric probability density function. {R 61cD,n
g'=B%eO$j:
Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability t{FlB!jv
density function at X with integer parameters M, K, and N. R~jHr
)0.#
Note: The density function is zero unless X is an integer. F;[T#N:~
)m{Ye0!RD
The size of Y is the common size of the input arguments. A scalar input UkHY[M7;
functions as a constant matrix of the same size as the other inputs. ,0~9dS
x-<)\ L&
See also hygecdf, hygeinv, hygernd, hygestat, pdf. i|}[A
vR=6pl$|~~
Reference page in Help browser l)w Hl%p
doc hygepdf RE=+ Dz{
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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： \, &co
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http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m FwY&/\J7V
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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。 T?1Du"d8
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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? MJCzo |w
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p = hygepdf(0:5,100,20,10) TsUOpEuX
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p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215 #8bsxx!s
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详细可参见： C? = P
http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 a9Z%JS]
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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 drd/ jH&
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x = 0:5 G0{H5_h
p = hygepdf(x,100,20,10); =rQP[ICs!
plot(x,p,':k*')
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