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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jq n
_ H]*~4F ans =
`P(Otr[6 GIs
*;ps7w NaN
x5Z(_hU oh @|*RU 查看了一下帮助 help hygepdf
n0T>sE -9 RaX :&PE HYGEPDF Hypergeometric probability density function.
/XeCJxo8 u/,ng &! Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
^! r<-J
density function at X with integer parameters M, K, and N.
2Nau]y]= Note: The density function is zero unless X is an integer.
?h1r6?Sug{ M ODi:jsl The size of Y is the common size of the input arguments. A scalar input
}zE
Qrfl functions as a constant matrix of the same size as the other inputs.
xnp5XhU yE3l%<;q See also hygecdf, hygeinv, hygernd, hygestat, pdf.
v"~0 3-SX #[<XN s!" Reference page in Help browser
xDtJ& 6uFw doc hygepdf
V\=QAN^ V= +wsc 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：
v;_k*y[VV$ BT3X7Cx http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m 6M) 4v{F &
6-8$ 直到发现这个例子后才清楚各个参数所代表的具体意义。
`;\<Fr Bq# l8u 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?
vf&Sk` Mu>WS)1lS p = hygepdf(0:5,100,20,10)
/bBFPrW ;v=v4f'+ p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
QV_e6r1t#m cCWk^ lF], 详细可参见：
h p< NVST http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 U 5f<4I ~4t7Q 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
,!{/Y7PmJ TQjM3Ri=V x = 0:5
|."thTO p = hygepdf(x,100,20,10);
Obl,Qa:5 plot(x,p,':k*')
