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
l~.ae,|7 NJRk##Z ans =
kZfa8w L]P |wZcVc t~ NaN
q# $A l /I(IT=kp 查看了一下帮助 help hygepdf
&Ba` 3V\M Wxx? iW , HYGEPDF Hypergeometric probability density function.
OrNi<TY> 2r4owB? Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
9ldv*9v density function at X with integer parameters M, K, and N.
jvv3;lWDL. Note: The density function is zero unless X is an integer.
F
jsnFX; MOi.bHCQJP The size of Y is the common size of the input arguments. A scalar input
xM"k qRZ functions as a constant matrix of the same size as the other inputs.
z|E/pm$^ L|A}A[ P See also hygecdf, hygeinv, hygernd, hygestat, pdf.
`f?v_Ui-$ ;/ l$&: Reference page in Help browser
Q]?r&%Y doc hygepdf
r)E9]"TAB ra2sYH1wr 超几何分布参数较多，这里关于三个参数的指代不详。又在互联网上查了相关资料，包括该函数的定义式：
,rc?,J1l Z]OXitt7 http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m B >2" O dNK Q&TC 直到发现这个例子后才清楚各个参数所代表的具体意义。
;;;aM:6\ [;~:',vHQf Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random?
FOz~iS\ 'Km
~3t p = hygepdf(0:5,100,20,10)
WZ,}]D #e) A p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
B /q/6Pp Av6 =q=D 详细可参见：
8$ 9Q=M http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 -hL 0}Wy$N `Tw DR6& 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
X )6}<A =)QtE|p,77 x = 0:5
=ie8{j2: p = hygepdf(x,100,20,10);
" ,k(* plot(x,p,':k*')
