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
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NaN
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MS& RWo B7{G 查看了一下帮助 help hygepdf
j2M(W/_ Y7)@(7G)\ HYGEPDF Hypergeometric probability density function.
c7IR06E y}HC\A77uD Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
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c" density function at X with integer parameters M, K, and N.
PWu2;JF Note: The density function is zero unless X is an integer.
V^+:U>$w uP2a\C,$ The size of Y is the common size of the input arguments. A scalar input
r_E)HL/A functions as a constant matrix of the same size as the other inputs.
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0QqzS See also hygecdf, hygeinv, hygernd, hygestat, pdf.
]?`p_G3O )>5k'1 Reference page in Help browser
5qSZ>DZ doc hygepdf
SYPMoE!U: H;|:r[d! 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:
CZRo{2!?U WUS9zK http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m _l= f94jMzH9z 直到发现这个例子后才清楚各个参数所代表的具体意义。
D])YP0|} gdE `UZ\ 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?
{dXBXC/Ju GPLt<K!<# p = hygepdf(0:5,100,20,10)
Z[S+L"0 TeCpT2!5j p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
cCGXB|9fYR *;E+9^:V 详细可参见:
@[lc0_b http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 .r5oN +?e /&as) 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
n o+tVm| /8t+d.r;/ x = 0:5
3,L3C9V' p = hygepdf(x,100,20,10);
.]s(c!{y plot(x,p,':k*')