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
4J1Q])G9 @:I/lg=Qd ans =
4 `F*] Ft =l +p nG NaN
^-_!:7TH] $;1~JOZh 查看了一下帮助 help hygepdf
u4'Lm+&O d\ f 5\Y HYGEPDF Hypergeometric probability density function.
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&~U K\q/JuDfc Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
;`+,gVrp density function at X with integer parameters M, K, and N.
L%"Mp (gZ Note: The density function is zero unless X is an integer.
q .7CPm+ |D~MS`~qd5 The size of Y is the common size of the input arguments. A scalar input
d?mdw
?| functions as a constant matrix of the same size as the other inputs.
N\?iU8w= #C`!yU6( See also hygecdf, hygeinv, hygernd, hygestat, pdf.
Yq_zlxd%F U PC& O Reference page in Help browser
:U s-^zVr doc hygepdf
cPXvT Vvs 0)NHjKP 超几何分布参数较多，这里关于三个参数的指代不详。又在互联网上查了相关资料，包括该函数的定义式：
".u?-xcbJ b/EvcN8 } http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m `dK\VK^ M: 6 cma5 直到发现这个例子后才清楚各个参数所代表的具体意义。
\Mi< ROp5 ` 6A"e Da Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random?
n7G$ gLX lV?SvXe p = hygepdf(0:5,100,20,10)
lVdE xR>H *Pl[a1= o p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
o\#C] pp {e^llfj$# 详细可参见：
)
l)5^7=W http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 =
7? 'S# 5c#L6 dA) 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
,Y!)V 'e) t + x = 0:5
g`j%jQuY p = hygepdf(x,100,20,10);
J}x5Ko@ plot(x,p,':k*')
