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
^=eC1 bQA wp@_4Iq1$ ans =
Il
[ ~ P4@`C{F5m NaN
%T]$kF++& A, F~*LXm 查看了一下帮助 help hygepdf
J$}]p ]A2E2~~G HYGEPDF Hypergeometric probability density function.
igo9~. (
unmf,y Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
`,'/Sdr density function at X with integer parameters M, K, and N.
kqCsEtm] Note: The density function is zero unless X is an integer.
Z5Lmg u@dvF zc The size of Y is the common size of the input arguments. A scalar input
Xr
<H^X functions as a constant matrix of the same size as the other inputs.
+% YBa'Lk n5=U.r See also hygecdf, hygeinv, hygernd, hygestat, pdf.
V22z-$cb & jqylX Reference page in Help browser
! 64Tx doc hygepdf
jRjeL'"G e@vtJaSu 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：
k\[(;9sf. HaVhdv 3L http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m | 'z 8>1 WGz)-IB!PE 直到发现这个例子后才清楚各个参数所代表的具体意义。
Imv#7{ndq %rb$tKk Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random?
a qEZhMy F6}RPk\=i p = hygepdf(0:5,100,20,10)
&P b:P?I p
XXf5adl< p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
#DgHF*GG+> *|S6iSn9R! 详细可参见：
vS\ 2zwb} http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 U,P>P+\@ -
]wT 果然与一般对超几何分布公式字母惯常表示方式有所不同。尝试将上述分布作图如下
SO6)FiPy!n XSC=qg$
x = 0:5
@?<[ //1 p = hygepdf(x,100,20,10);
kL1<H%1' plot(x,p,':k*')
