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
/p>[$`Aq
pr"flRQr# ans =
d(!N$B\[5T `g=~u{ 0 NaN
k-U/x"Pl ,b4&$W]. 查看了一下帮助 help hygepdf
{aSq3C<r S6mmk&n HYGEPDF Hypergeometric probability density function.
tTgW^&B zvD5i,I Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
#!/Nmd=Nj density function at X with integer parameters M, K, and N.
4Z ] 35* Note: The density function is zero unless X is an integer.
p!ErH]lH hd~rC*I The size of Y is the common size of the input arguments. A scalar input
d%hA~E1rR functions as a constant matrix of the same size as the other inputs.
2"O Y]d 6,PL zZ5 See also hygecdf, hygeinv, hygernd, hygestat, pdf.
=Ug_1w E` |qFG< Reference page in Help browser
.yPx'_ e doc hygepdf
: +Kesa :E -+> am? 超几何分布参数较多，这里关于三个参数的指代不详。又在互联网上查了相关资料，包括该函数的定义式：
RHbwq] gL` SZr9 http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m @H h"Y1B In&vh9Lw 直到发现这个例子后才清楚各个参数所代表的具体意义。
/`> P |J }b`*%141 Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random?
H[
q{R I>a a'em p = hygepdf(0:5,100,20,10)
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28* }^7V^W p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
SO/]d70HG CvJEY 详细可参见：
Oe`t! &v http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 +b W| Q>u (rn x56I$ 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
4)I#[&f ]||=<!^kn x = 0:5
U@nwSfp:G p = hygepdf(x,100,20,10);
JuSS5 _& plot(x,p,':k*')
