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
(Xq )p y9 '=G|Sq^aO ans =
WeQk<y EVVP]ND NaN
q&/Yg,p\ \7l-@6 '7 查看了一下帮助 help hygepdf
qLT>Mz)$ % Yl#Rib HYGEPDF Hypergeometric probability density function.
kMOpi =Z1 ( ''M{n Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
we;G]`@? density function at X with integer parameters M, K, and N.
I>[RqG Note: The density function is zero unless X is an integer.
fe_yqIdk |&[L? The size of Y is the common size of the input arguments. A scalar input
-"h;uDz|z functions as a constant matrix of the same size as the other inputs.
Pp`*]Ib `}l JH i See also hygecdf, hygeinv, hygernd, hygestat, pdf.
{FIXc^m ' 8- _Q FgY Reference page in Help browser
7_mw%|m6@ doc hygepdf
_:-ha?W$;y V {pj~D.E 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：
OV%Q3$15 H N. 3 http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m &*7?)eI!i MwR 0@S}* 直到发现这个例子后才清楚各个参数所代表的具体意义。
0LfU=X0#7 jGEt+\"/QJ 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?
^H2-RBE# \yd
s5g!: p = hygepdf(0:5,100,20,10)
@:U+9[ q*7zx_ o p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
%ix)8+Eb }p!HT6 tZ 详细可参见：
)~+ e`q http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 =7 C%P%yt mXUGe:e8 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
Tjl:|F8 BvR-K\rx x = 0:5
'{J&M|<A p = hygepdf(x,100,20,10);
B:e
@0049 plot(x,p,':k*')
