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
nN{DO:_o SdlO]y9E ans =
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2@a 'n@- %.$!VTO" 查看了一下帮助 help hygepdf
_K#7#qp2 _ooHB>sH HYGEPDF Hypergeometric probability density function.
VzSkqWF/" @TALZk'% Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
la{?&75] density function at X with integer parameters M, K, and N.
J8~h Iy6] Note: The density function is zero unless X is an integer.
w~B1TfqNo _W(xO
|,M The size of Y is the common size of the input arguments. A scalar input
;b [>{Q; functions as a constant matrix of the same size as the other inputs.
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W2jA See also hygecdf, hygeinv, hygernd, hygestat, pdf.
%@:>hQ2 ; #6@hVR. Reference page in Help browser
PNAvT$0LaZ doc hygepdf
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3E 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：
15 {^waR6 s&ox%L 4 http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m Q)aoc.f!v L?u {v X 直到发现这个例子后才清楚各个参数所代表的具体意义。
|h $Gs2 ^r}Uu~A> Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random?
x} a?B wrJQkven- p = hygepdf(0:5,100,20,10)
ruagJS)+ vh O h3 p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
?5" >5 0 eJqx,W5MK] 详细可参见：
bP$e1I3` http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 ?:vg`m!* |6-9vU!LK? 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
<6]Hj2 {0j,U\ kb x = 0:5
$]?pAqU\ p = hygepdf(x,100,20,10);
x y>$^/[$ plot(x,p,':k*')
