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
!y[3]8Xxv "
" %#cDR ans =
fRNP#pi0u |}Ph"g2D, NaN
t9` Ed>a vRr9%z x 查看了一下帮助 help hygepdf
moG~S] X"<|Z]w HYGEPDF Hypergeometric probability density function.
\fi}Q\|C ~kb{K; Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
{7X~!e|w density function at X with integer parameters M, K, and N.
}_%P6 Note: The density function is zero unless X is an integer.
Qxq-Mpx{ E9$H nj+m The size of Y is the common size of the input arguments. A scalar input
L~&" aF/b functions as a constant matrix of the same size as the other inputs.
eY}V9*.v Pa&4)OD See also hygecdf, hygeinv, hygernd, hygestat, pdf.
j^ EbO3 28 UV DG1? Reference page in Help browser
>r}Vf9 5[N doc hygepdf
^y Vl"/ zP nC=h|g 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：
S(t{&+Wc (/?R9T[V&^ http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m :Q- F9o
J {Hk/1KG> 直到发现这个例子后才清楚各个参数所代表的具体意义。
0roCP =;
] .5O X84 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?
- _t&+5] WQKj]:qk0 p = hygepdf(0:5,100,20,10)
ZqK]jT6V/X AP w6 p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
HJ@ 5 B" l RND 详细可参见：
(oYW]c}G, http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 \_U* t! M[s\E4l:t 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
t)r1"o A &HL{LnLP@/ x = 0:5
p+<}Y DMb p = hygepdf(x,100,20,10);
y x ;h plot(x,p,':k*')
