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
~A>3k2 N/e Ca?pK_Y ans =
Kgk9 p`C( 3U1x KF NaN
ikyvst>O Z+ I[ 查看了一下帮助 help hygepdf
[rE,fR g&riio7lx HYGEPDF Hypergeometric probability density function.
j"}alS`- wy vs#T Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
N@;6/[8 density function at X with integer parameters M, K, and N.
C Z|Y o Note: The density function is zero unless X is an integer.
{#Mz4s`M a+r0@eFLc The size of Y is the common size of the input arguments. A scalar input
@0n #Qs|E! functions as a constant matrix of the same size as the other inputs.
@i6D&e= CQ#p2 See also hygecdf, hygeinv, hygernd, hygestat, pdf.
Jq /([
E83{4A4 Reference page in Help browser
\>:(++ g doc hygepdf
xxiEL2"`> #sA E Ik/ 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：
rw 8db' 0Oe@0L%^3" http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m ]>*Z 1g; :mY(d6#A> 直到发现这个例子后才清楚各个参数所代表的具体意义。
\u",bMQF vF1] L]z:? 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?
0m51nw~B Ur]5AJ p = hygepdf(0:5,100,20,10)
)jCAfdnCs YX@[z
5* p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
YuLW]Q?v =(.HO:# 详细可参见：
g%[lUxL http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 TpZ)v.w~l7 d}ue/hdw 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
pkBm AJb@ Q]IpHNt[> x = 0:5
U,aV {qz p = hygepdf(x,100,20,10);
NWb,$/7T plot(x,p,':k*')
