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
S) [`Bm dOFxzk,g&R ans =
otX B:a }XiS:
NaN
D'>yu" eD* "#O)W 查看了一下帮助 help hygepdf
+[JGi"ca eA>O<Z1> HYGEPDF Hypergeometric probability density function.
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s m&OzT~?_>N Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
DB yRP-TH density function at X with integer parameters M, K, and N.
Y>+\:O
Note: The density function is zero unless X is an integer.
Ftm%@S ? Y XH9Q@Gn The size of Y is the common size of the input arguments. A scalar input
k[N46=u functions as a constant matrix of the same size as the other inputs.
v.+-)RLQg f;6a4<bz See also hygecdf, hygeinv, hygernd, hygestat, pdf.
A8OV3h6] LD WF c_ Reference page in Help browser
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By doc hygepdf
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_tN"<9v. 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：
K ^1bR(a <!&&Qd-d6H http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m z@cL<.0CE vcAs!ls+ 直到发现这个例子后才清楚各个参数所代表的具体意义。
S@zsPz w gydPy* 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?
PK u+$ UR?[ba_h p = hygepdf(0:5,100,20,10)
;y?,myO LI?rz<H!D p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
{3C~cK{ &?*M+q34 详细可参见：
5-bd1!o http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 7,_N9Q]rB [[?:,6I 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
|J2R w f G7`7e@{ x = 0:5
6d,jR [JP p = hygepdf(x,100,20,10);
gmWRw{nS+ plot(x,p,':k*')
