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
x[a'(5PwY ^B6`e^ < ans =
_6 /Qp`s tQCj)Ms 'X NaN
" # J}A0 $WM8tF?H 查看了一下帮助 help hygepdf
y ( ldO;. 6%z`)d HYGEPDF Hypergeometric probability density function.
?xf~!D X
&09 Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
`;T? 9n density function at X with integer parameters M, K, and N.
3?]S,~!F Note: The density function is zero unless X is an integer.
I$F\ (]"@ R =QM; The size of Y is the common size of the input arguments. A scalar input
34]%d<;A functions as a constant matrix of the same size as the other inputs.
?/ ^VOj4& "9.6\Y\* See also hygecdf, hygeinv, hygernd, hygestat, pdf.
SaTEZ. =1_j aDp Reference page in Help browser
]#+5)[N$> doc hygepdf
_4g}kL02. 1 w6. 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：
2%*|fF}I Z*;*I< - http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m UfO'. 8*v %{c2lyw 直到发现这个例子后才清楚各个参数所代表的具体意义。
o^N%;d1%E /}[zA@ 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?
Y}*Ctdrl g9! d pP p = hygepdf(0:5,100,20,10)
8APTk KF*B p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
_6|
/P7" 9 eksCxFg 详细可参见：
?T~3B]R http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 L'zdsa}Et `z5v}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
X/K| WOO6 &Qz"nCvJ x = 0:5
F&-5&'6G+ p = hygepdf(x,100,20,10);
G`&'Bt{Z* plot(x,p,':k*')
