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
x5BS|3W$a jqc}mI\# ans =
5~@-LXqL 5)lcgvp NaN
A@)Q-V8*9s iC=>wrqY> 查看了一下帮助 help hygepdf
o
/[7Vo ;M4[Liw~O HYGEPDF Hypergeometric probability density function.
] Z8u0YtM) /}8Au$nA Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
Pd" c*n&9 density function at X with integer parameters M, K, and N.
c]aU}[s1 Note: The density function is zero unless X is an integer.
[Tp?u8$p` qpYgTn8l7 The size of Y is the common size of the input arguments. A scalar input
`?(J(H functions as a constant matrix of the same size as the other inputs.
n-cI~Ax+4 "5~?`5Ff See also hygecdf, hygeinv, hygernd, hygestat, pdf.
oMj"l#a* E OXkMr Reference page in Help browser
S3Gr}N doc hygepdf
J 'X}6Q Sl, DZ! 超几何分布参数较多，这里关于三个参数的指代不详。又在互联网上查了相关资料，包括该函数的定义式：
@Xl(A]w%! 'WP~-}( http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m yVmp,""a WX? nq'nr 直到发现这个例子后才清楚各个参数所代表的具体意义。
1bCE~,tD \EVT*v=}/ Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random?
/-[vC$B" }_zN%Tf~ p = hygepdf(0:5,100,20,10)
@gK`RmhGE5 9d#?,:JG p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
JR.)CzC zP #:Tv' 详细可参见：
K?' m#}] http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 Yp;Z+!!UZ Ne Y*l 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
E0 +L?(; MLH CB Ri x = 0:5
+?U[362 > p = hygepdf(x,100,20,10);
%QEBY>|lI plot(x,p,':k*')
