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
IZOO>-g'f Z:.*fs5 ans =
h_\OtoRa H-jxH,mJmW NaN
<Xb$YB-c cd]def[d 查看了一下帮助 help hygepdf
*Z2#U ?_ @H61 ^K< HYGEPDF Hypergeometric probability density function.
CM4#Nn=i~ rHJtNN8$k Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
[BuAJ930#5 density function at X with integer parameters M, K, and N.
tqzr + Note: The density function is zero unless X is an integer.
@f`s%o YWhp 4`m The size of Y is the common size of the input arguments. A scalar input
uL
|O < functions as a constant matrix of the same size as the other inputs.
grTwo ~$]Puv1V> See also hygecdf, hygeinv, hygernd, hygestat, pdf.
+
;_0:+// :aWC6"ik-W Reference page in Help browser
:[?65q{ doc hygepdf
i9 v|*ZM" *_/n$&
I%& 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：
a 3C\? 5 nJcY>Rp? http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m y 4Lh:;
/PZ xF 直到发现这个例子后才清楚各个参数所代表的具体意义。
To =JE}jzo g96]>]A<{ 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?
r Fhi:uRV <~n%=^knE p = hygepdf(0:5,100,20,10)
/dwj:g0y j
W/*-: p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
Y}
cr E/ lX/ :e= 详细可参见：
A9o"L.o) http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 '4,>#D8@O oD=+ 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
^c?$$Tq O:jaA3 x = 0:5
ep G!V#I p = hygepdf(x,100,20,10);
`qhZZ{s)1U plot(x,p,':k*')
