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
_R(Zvs OZ PeIi@0vA ans =
XK\nOHLS 9=$ p V== NaN
]e-QN I evZP*N~G 查看了一下帮助 help hygepdf
TU)Pi.Aa >lM/\HO2 HYGEPDF Hypergeometric probability density function.
/"="y'Wx e;~(7/1 Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
V?* fl^f density function at X with integer parameters M, K, and N.
`D= OEc Note: The density function is zero unless X is an integer.
k(tB+k!vH\ 72RTEGy The size of Y is the common size of the input arguments. A scalar input
^W=hs9a+F functions as a constant matrix of the same size as the other inputs.
z-K};l9y 0TV16 -- See also hygecdf, hygeinv, hygernd, hygestat, pdf.
%"c;kvw }\H. G Reference page in Help browser
c{to9Lk.# doc hygepdf
h`! 4`eI Ux?G:LLz 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：
|UlR+'rl E$ 8-8[ http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m Ow1+zltgj- Pl|I{l*o(` 直到发现这个例子后才清楚各个参数所代表的具体意义。
Y:+:>[F q2 |z
\ 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?
M@q)\UQ' k}kwr[ p = hygepdf(0:5,100,20,10)
aVV E 2:M t3}_mJ p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
0V8G9Gj h$~$a;2cR 详细可参见：
*a_QuEw _k http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 S=<
]u A ?~4Pe 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
ZFX}=?+ T|oDJ]\J x = 0:5
&SZAe/3+ p = hygepdf(x,100,20,10);
M D1d plot(x,p,':k*')
