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
j%Cr)' H? c~=y D:$ ans =
(9X>E+0E {+.ai 8 NaN
SyWLPh G"'[dL)N> 查看了一下帮助 help hygepdf
oP 0ZJK&; n! >#o 1Qr HYGEPDF Hypergeometric probability density function.
N`Q[OFe e52y}'L Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
(wtw1E5X density function at X with integer parameters M, K, and N.
T M1D|H Note: The density function is zero unless X is an integer.
^^m3
11 = m EM/}]2 The size of Y is the common size of the input arguments. A scalar input
M^$liS.D functions as a constant matrix of the same size as the other inputs.
f|&ga'5g& IxxA8[^V See also hygecdf, hygeinv, hygernd, hygestat, pdf.
&\_cU?0d 5csqu^/y Reference page in Help browser
3 IK +&hk doc hygepdf
eK]$8l|LI nYF *f 超几何分布参数较多，这里关于三个参数的指代不详。又在互联网上查了相关资料，包括该函数的定义式：
xqA XfJ. J% t[ { http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m yN Bb(!u ?g5u#Q> ! 直到发现这个例子后才清楚各个参数所代表的具体意义。
! UV/p"CfX 1 iWe&I: Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random?
F|seBBu 5%5z@Ka p = hygepdf(0:5,100,20,10)
@A-^~LoP. 2' 8$I}h p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
Gw;[maM!%` /h!Y/\ kI 详细可参见：
Owa]ax5 http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 4GY:N6qe ' Yiq8 >| 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
G \S >H 6a=Y_fma x = 0:5
yM8<)6= p = hygepdf(x,100,20,10);
A`D^}F6 plot(x,p,':k*')
