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
2'^OtM, Zz*mf+ ans =
.N><yQ-j3' ,HO/Q6;N NaN
AQNx% SFPIr0 u 查看了一下帮助 help hygepdf
vFvu8*0 6 8br HYGEPDF Hypergeometric probability density function.
=/'*(\C2 ^d $e^cU Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
8}`8lOE7 density function at X with integer parameters M, K, and N.
K[;,/:Y Note: The density function is zero unless X is an integer.
VKf HN_m* s L`D }_: The size of Y is the common size of the input arguments. A scalar input
L$?~TY functions as a constant matrix of the same size as the other inputs.
V'h z1roe #w?%&,Kp See also hygecdf, hygeinv, hygernd, hygestat, pdf.
Oy`\8*Uy__ 5Fm? ,^ Reference page in Help browser
nk,Mo5iqV doc hygepdf
n[S*gX0 ..{^"`F Q 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：
.0;k|&eBD f2e$BA http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m m<LzB_ G\ g Y^TBR0?m 直到发现这个例子后才清楚各个参数所代表的具体意义。
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Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random?
qvE[_1QCc 1`J N p = hygepdf(0:5,100,20,10)
-ns a3P U5%]nT"[] p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
\ bmboNe ^
/eSby 详细可参见：
Ps 5wQaS http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 aZ3 #g e7AI&5Eg{ 果然与一般对超几何分布公式字母惯常表示方式有所不同。尝试将上述分布作图如下
m`0{j1K 6C}Z1lZl x = 0:5
& I_!&m~ p = hygepdf(x,100,20,10);
_^$b$4) plot(x,p,':k*')
