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
T sW6 w NVZNQ { ans =
bO3KaOC8N N ] /d NaN
J&1N8Wk ) e ;r-}U 查看了一下帮助 help hygepdf
CGl+!t{ #| E. y^IC HYGEPDF Hypergeometric probability density function.
t1s@Ub5);I W?Abx Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
9gayu<J density function at X with integer parameters M, K, and N.
tzJt d Note: The density function is zero unless X is an integer.
5j5t?G;d, ` &7? +s The size of Y is the common size of the input arguments. A scalar input
qZ1PC> functions as a constant matrix of the same size as the other inputs.
yE{UV>ry i.,B
0s] Z See also hygecdf, hygeinv, hygernd, hygestat, pdf.
O4mWsr N Z9,9 Reference page in Help browser
vu >@_ hv doc hygepdf
m]pvJJ@ o!0a8i 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：
Ll48)P{+}V me\)JCZpb{ http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m ?IO/zkeXg tvCTC ey 直到发现这个例子后才清楚各个参数所代表的具体意义。
D"5~-9< ~,1X>N" 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?
kIo ?<=F8T ]HT>-Ba;{h p = hygepdf(0:5,100,20,10)
`o'sp9_3 Py<vN! p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
^E*C~;^S 24l9/v' 详细可参见：
^>u GbhBp http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 c~;.m<yrf Hb4rpAeP 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
<!$Cvx\U q \Z1-sl~s x = 0:5
"$9ZkADO p = hygepdf(x,100,20,10);
]z NL+]1_ plot(x,p,':k*')
