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
$i1>?pb3 z/ c'Z#w% ans =
2dp*>F0L -jcrXskb&N NaN
%8bF QNd 2c*VHIl; 查看了一下帮助 help hygepdf
;ph+ZV Mt7X<?GZm HYGEPDF Hypergeometric probability density function.
:O>Nd\UtO 8EW `*+%= Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
cG~_EX$ density function at X with integer parameters M, K, and N.
zWKrt.Dg Note: The density function is zero unless X is an integer.
bi4^ zaCEE J8 `1V `$ The size of Y is the common size of the input arguments. A scalar input
m \R@.jkZ functions as a constant matrix of the same size as the other inputs.
XY$cx~ D 9@<#2- See also hygecdf, hygeinv, hygernd, hygestat, pdf.
f"} 0j|Gg Z.cG`Km* Reference page in Help browser
Z(Ls#hp doc hygepdf
<E (- QJ |zr)hC
超几何分布参数较多，这里关于三个参数的指代不详。又在互联网上查了相关资料，包括该函数的定义式：
{4 V:[*3 9v5.4a} http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m {kY`X[fvZ dxae2 t V 直到发现这个例子后才清楚各个参数所代表的具体意义。
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xj|lr Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random?
T^f&58{ 7 YA/H;707l p = hygepdf(0:5,100,20,10)
DI"dY
ug# R, (+NT$ p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
:">~(Rd ZH e2VL/>y` 详细可参见：
Fr E/K _L http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 l zQ&)7 ` @N:3`[oB 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
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H x = 0:5
nu1 w: p = hygepdf(x,100,20,10);
+ $pO plot(x,p,':k*')
