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
-cq ~\m^6 P]dDTh~e~ ans =
f()^^ +
4uU(t NaN
;}|.crMF U@Aq@d+n 查看了一下帮助 help hygepdf
[k."R@? r<C^hs&] HYGEPDF Hypergeometric probability density function.
PO)5L Av+
w>~/3 Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
]e? * 7T] density function at X with integer parameters M, K, and N.
L=HL1Qe$G] Note: The density function is zero unless X is an integer.
IFpmf0;^ 1Rp |*> The size of Y is the common size of the input arguments. A scalar input
V !FzVl=G functions as a constant matrix of the same size as the other inputs.
E8NIH!dI jX+L I See also hygecdf, hygeinv, hygernd, hygestat, pdf.
7Dm^49H TU[f"!z^ Reference page in Help browser
_DJ0 MR~3 doc hygepdf
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LaZ5 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：
-P'>~W,~ rM>&! ?y+ http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m f<kL}B+,Og JmN;v|wF:c 直到发现这个例子后才清楚各个参数所代表的具体意义。
XTZWbhNF uLL#(bhDr 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?
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_Zs bdcu O)3 p = hygepdf(0:5,100,20,10)
zWjGGTP~3& hk,Q=}; p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
K= 06I vv%Di.V 详细可参见：
D-,sF 8{ i http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 Saz+ GQ G nMVThN*I g 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
df8rf8B- MgtyO3GUAD x = 0:5
9 lA YCsX p = hygepdf(x,100,20,10);
Yq5}r?N plot(x,p,':k*')
