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
i'z (`" 7w.9PNhy ans =
!JbWxGN`jn V L;< +C~ NaN
ORhvo,.u I~ e,'] 查看了一下帮助 help hygepdf
#NWS)^&1b vA *Q}]Ov HYGEPDF Hypergeometric probability density function.
j"n"=rTTQ U4h5K}j4 Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
< mp_[-c density function at X with integer parameters M, K, and N.
n4 o}}tI Note: The density function is zero unless X is an integer.
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4 The size of Y is the common size of the input arguments. A scalar input
;]T;mb> functions as a constant matrix of the same size as the other inputs.
7Jn %c<s {tUxRX See also hygecdf, hygeinv, hygernd, hygestat, pdf.
z7R2viR[ ^AC2 zC Reference page in Help browser
r?HbApV P doc hygepdf
sZ#U{LI 3+H[S#e:Z 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：
[n&SA]a %wN*Hu~E http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m 9S8V`aC yw*|
H T 直到发现这个例子后才清楚各个参数所代表的具体意义。
af|x(:!H URj2 evYW 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?
uuYeXI; [" 15~9 p = hygepdf(0:5,100,20,10)
N_?15R7h 15M!erT p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
N 'YzCq;M ?4#wVzuzA 详细可参见：
bCV_jR+ http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 S%3&Y3S O T .bXr~ 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
w6|l ~.$= 4c@_u8 x = 0:5
t_ id/ p = hygepdf(x,100,20,10);
FA1h!Vit plot(x,p,':k*')
