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
{J)gS phA{jJy? ans =
F6D Vq8f9 UY *Z`$ NaN
{P ?p*2J' @Z""|H"0 查看了一下帮助 help hygepdf
!*q Q 7 .db:mSrL HYGEPDF Hypergeometric probability density function.
KCa @0 #8v l2qWbi Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
xOxyz6B\ density function at X with integer parameters M, K, and N.
Lrt~Q:z2u Note: The density function is zero unless X is an integer.
rV%;d[LB gi_f8RP=2a The size of Y is the common size of the input arguments. A scalar input
<gvgr4@^yR functions as a constant matrix of the same size as the other inputs.
04 X/(74 }*P;kV See also hygecdf, hygeinv, hygernd, hygestat, pdf.
ZI :wJU:f hR [_1vuIu Reference page in Help browser
Y!u">M#@ doc hygepdf
9-=kVmT&g }vF=X A 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：
>Zm|R|{BE 8"wavh|g4 http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m 2mthUq9b* 7W/55ZTmJ 直到发现这个例子后才清楚各个参数所代表的具体意义。
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= 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?
WR* <| DQN"85AIZ p = hygepdf(0:5,100,20,10)
We"\nOP gHvkr?Cg p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
B]#iZ, Tp DT]3q4__Q 详细可参见：
UPuG&A#VV http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 @G>&Gu;5 :7qJ[k{g 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_)WUS.c *U,W4>(B x = 0:5
y
0fI7:e3 p = hygepdf(x,100,20,10);
2 :^ plot(x,p,':k*')
