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
&4|]VOf 1="]'!2Is ans =
SF*mY=1 9) ]`le NaN
Jj [3rt?8 l![ 79 eFp 查看了一下帮助 help hygepdf
h ChO qjkWCLOd HYGEPDF Hypergeometric probability density function.
M !"Q7 >d 5JVBDA^#om Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
SaF0JPm4z density function at X with integer parameters M, K, and N.
u`N rg< Note: The density function is zero unless X is an integer.
5)S; R, ~FYC'd The size of Y is the common size of the input arguments. A scalar input
flqr["czwK functions as a constant matrix of the same size as the other inputs.
D9NR M;v G@D;_$a See also hygecdf, hygeinv, hygernd, hygestat, pdf.
0 fT* O ym6Emf] Reference page in Help browser
/];N 1 doc hygepdf
,e1c,} P;25 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：
,Aq, f$5V 3=ME$%f http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m x C _3&. [= E=H*j 直到发现这个例子后才清楚各个参数所代表的具体意义。
;WN% tI) M<Z#4Gg#4 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?
l2Py2ZI-b V4"o.G3\o p = hygepdf(0:5,100,20,10)
e[T3,2C @]X!#&2> p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
~!TrC <ft nY1PRX\ 详细可参见：
Bq~S=bAB>R http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 !lEV^SQJs K6B6@ 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
AX @bM ! $iwU3~< x = 0:5
aRWj+[[7y p = hygepdf(x,100,20,10);
4xs>X7 plot(x,p,':k*')
