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
xF Ths,w sUc[!S:/ ans =
CYE[$*g6y <+q`Dk NaN
Nr XIaN \ILNx^$EL 查看了一下帮助 help hygepdf
'&,p>aM pL[3,.@WA HYGEPDF Hypergeometric probability density function.
B/@LE{qUn r_Ou\|jU Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
qyVARy density function at X with integer parameters M, K, and N.
Iq,h}7C8' Note: The density function is zero unless X is an integer.
}ff^^7_ H{N},B The size of Y is the common size of the input arguments. A scalar input
PknKzrEG:> functions as a constant matrix of the same size as the other inputs.
~4Fz A,, V O {z)_ See also hygecdf, hygeinv, hygernd, hygestat, pdf.
z^tzP~nI %vZHHBylu Reference page in Help browser
Ths~8{dMb doc hygepdf
S!$S'{f< 6qTMHRI 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：
v,QvCozOz :8/ 6dx@Y( http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m Q=DMfJ" RR+kjK? 直到发现这个例子后才清楚各个参数所代表的具体意义。
=Gz s+6A8 t&w.Wc X) 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?
8pr toCB I2RXw p = hygepdf(0:5,100,20,10)
Gukvd6-g9b _fY9u2Y p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
"PN4{ "`V DOFW"Sp E 详细可参见：
5+oY c- http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 $")Gd@ aR )h0>e9z>Y 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
4t%Lo2v!X% I9xu3izAmR x = 0:5
LQ% QFfC p = hygepdf(x,100,20,10);
9__Q-J plot(x,p,':k*')
