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
>[|Y$$ /WX
0}mWu ans =
=ijVT_|u0 (D 5.NB%@ NaN
ui#K`.dn Xs7x Z$ 查看了一下帮助 help hygepdf
c (Gl3^ Jg\1(ix HYGEPDF Hypergeometric probability density function.
mrvPzoF,] KJ&~z? X Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
jWL; ElM' density function at X with integer parameters M, K, and N.
uEPdL':}2 Note: The density function is zero unless X is an integer.
DeTD.)pS t<QSp6n"" The size of Y is the common size of the input arguments. A scalar input
#(KE9h% functions as a constant matrix of the same size as the other inputs.
:P1/ kYg g =)djXW See also hygecdf, hygeinv, hygernd, hygestat, pdf.
4`mF6%UC Oe^oigcM Reference page in Help browser
WOaj_o doc hygepdf
NEG&zf n :P 5m9T 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：
e//q`?ys 3S_H hvB http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m #MhieG5 GE0,d 直到发现这个例子后才清楚各个参数所代表的具体意义。
.oR _r1\y |f.R]+ cH 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?
oA1d8*i^E D >~S-] p = hygepdf(0:5,100,20,10)
!gfz 4f & qr~= S p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
~>]/1JFz c[xH: $G?Y 详细可参见：
k}o*=s> M http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 d].(x)|st [8J/# !B
果然与一般对超几何分布公式字母惯常表示方式有所不同。尝试将上述分布作图如下
T)QT_ST.9 }N6r/
VtOQ x = 0:5
*`HE$k! p = hygepdf(x,100,20,10);
F;&a=R!. plot(x,p,':k*')
