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
ZW$PJmz 2YD;Gb[8 ans =
}VlX!/42 /=9t$u| NaN
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8m 75j `3wzu 查看了一下帮助 help hygepdf
:^+ aJ] N`7) 88>w HYGEPDF Hypergeometric probability density function.
>E&m Np sGjYL>* Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
EN wDW# U9 density function at X with integer parameters M, K, and N.
;6g &_6 Note: The density function is zero unless X is an integer.
,}i`1E 1= X OQj?Q7)U The size of Y is the common size of the input arguments. A scalar input
&BnK[Q8X functions as a constant matrix of the same size as the other inputs.
{O-,JCq / #!d@;= [\ See also hygecdf, hygeinv, hygernd, hygestat, pdf.
9K*yds J>(I"K% Reference page in Help browser
R=jIVw' doc hygepdf
H tIl;E 6$TE-l 超几何分布参数较多，这里关于三个参数的指代不详。又在互联网上查了相关资料，包括该函数的定义式：
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GU99!.$ http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m >'4Bq*5> qk pnXQ 直到发现这个例子后才清楚各个参数所代表的具体意义。
}~Z1C0 t +@),Fk_ 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?
*Z"9Q X ", b}-B p = hygepdf(0:5,100,20,10)
qF m=(J% [m7^Euury p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
f)x^s$H ;W6P$@'zs 详细可参见：
'ojI _%9< http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 7(<6+q2~ *k:Sg*neVq 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
/an$4?":~ ZSj^\JU x = 0:5
HMbF#!E p = hygepdf(x,100,20,10);
FCv3ZF?K plot(x,p,':k*')
