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
P_qxw-s O}D]G%,m ans =
Ohjqdv@ }vm17`Gfy NaN
a. gu ad"&c*m[ 查看了一下帮助 help hygepdf
e%qMrR 7f`jl/ HYGEPDF Hypergeometric probability density function.
plp).Gq # - kyZ Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
ucMl>G'!gX density function at X with integer parameters M, K, and N.
:Z/ i g% Note: The density function is zero unless X is an integer.
,{.&xJ$ +)V6" XY-( The size of Y is the common size of the input arguments. A scalar input
O 4}cv functions as a constant matrix of the same size as the other inputs.
(K2 p3M^ sd=i!r)ya See also hygecdf, hygeinv, hygernd, hygestat, pdf.
Pajr`gU mMa7Eyaf Reference page in Help browser
?$o8 =h doc hygepdf
|D^[ ]*cEH v=/V<3 超几何分布参数较多，这里关于三个参数的指代不详。又在互联网上查了相关资料，包括该函数的定义式：
1 dKLNE ,2]6cP(6qQ http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m (57x5qP
X B gE]xm 直到发现这个例子后才清楚各个参数所代表的具体意义。
#7g~U m%p 0 "> # h Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random?
k|BEAdQ%M F 6SIhf.; p = hygepdf(0:5,100,20,10)
d$>1 2>> Maq{H` p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
]{;K|rCR- y[}BFUy 详细可参见：
sGzd c http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 6%5A&& O(b TX 12$p\ 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
b9:E0/6
LtNG<n)_BH x = 0:5
kiXa2Yn*(d p = hygepdf(x,100,20,10);
OtnYv plot(x,p,':k*')
