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 eU};Pv 6}L[7~1
ans =
CYEqH2"3 'iXjt
MX NaN
[LL"86D y`mE s j 查看了一下帮助 help hygepdf
QD+dP nZu [@rZ.Hsl HYGEPDF Hypergeometric probability density function.
'|J-8" A8e b{qv Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
t<|=- density function at X with integer parameters M, K, and N.
?.v!RdM+ Note: The density function is zero unless X is an integer.
$*xnq%A .m;1V6 The size of Y is the common size of the input arguments. A scalar input
{h&*H[Z z functions as a constant matrix of the same size as the other inputs.
_S,2j_R9 O(~`fN?n See also hygecdf, hygeinv, hygernd, hygestat, pdf.
q}ZZqYk k:m~'r8z
Reference page in Help browser
uE VRk9nb doc hygepdf
^-~.L: }q 7T_g?!sdMh 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：
MZn7gT0 'RQZU*8 http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m _<pG}fmR }C2I9Cl 直到发现这个例子后才清楚各个参数所代表的具体意义。
> :!faWX u 6 l 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?
x2Y1B Tx/ p = hygepdf(0:5,100,20,10)
9{70l 539 A.
U< p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
"LaNXZ9 ~< Gs<c}z 详细可参见：
gLl?e8[F http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 g}ciG!0 q&jZmr 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
D<L ]' K&BlWXT x = 0:5
O5Yk=-_m p = hygepdf(x,100,20,10);
baR{ plot(x,p,':k*')
