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
K | Y r k2*^W&Z ans =
'(u [ Ra_6}k NaN
zYSXG -k
[?Aq#av 查看了一下帮助 help hygepdf
}(TZ}* d C2eei're HYGEPDF Hypergeometric probability density function.
94|BSxc tp*AA@~ Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
h+ELtf density function at X with integer parameters M, K, and N.
)X| uOg&| Note: The density function is zero unless X is an integer.
HPwmi[ l!q i:H<=1 The size of Y is the common size of the input arguments. A scalar input
ycCEXu2F functions as a constant matrix of the same size as the other inputs.
zc,fJM O2R v^la See also hygecdf, hygeinv, hygernd, hygestat, pdf.
}[l`R{d5q> t]" 3vE> Reference page in Help browser
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4- doc hygepdf
2f I?P Z: 9" 7^+ 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：
KH2a 2 nKkI http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m WZ"x\K-; 0xC {Lf& 直到发现这个例子后才清楚各个参数所代表的具体意义。
U4O F{ A*~zdZ p 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?
/_w oCLwQ# |7UR_(}KC p = hygepdf(0:5,100,20,10)
`N8A{8$qv ?OvtR:h C p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
eSywWSdf0 CQzJ_aSJ ( 详细可参见：
hMeE@Q0 http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 Kv!CL9^LX7 + lU:I 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
%,-vmqr ],&WA?>G x = 0:5
D`r:` p = hygepdf(x,100,20,10);
8TC%]SvYim plot(x,p,':k*')
