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
vJtQ&,zG -XPGl ans =
7V 2% $qP9EZ]JC NaN
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rfXM*h 查看了一下帮助 help hygepdf
! r.X. C S]K^wj[ HYGEPDF Hypergeometric probability density function.
Mf%/t HK IW$&V` `v Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability
QI0ARd S density function at X with integer parameters M, K, and N.
u17Da9@; Note: The density function is zero unless X is an integer.
",#rI+ el ["Z]K'?P The size of Y is the common size of the input arguments. A scalar input
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X Tc%Z functions as a constant matrix of the same size as the other inputs.
/U N%P2>^1 I]~xs0$4# See also hygecdf, hygeinv, hygernd, hygestat, pdf.
M GN*i9CE TG{ =~ 2
Reference page in Help browser
6Ck?O/^ doc hygepdf
t=xO12Z '=\]4?S 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：
h'MX{Wm. jdXkU http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m j MW|B !+U#^ 2Gz 直到发现这个例子后才清楚各个参数所代表的具体意义。
%nFZA)B[ Q\m"n^ XN 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?
` *$^rQS yc_(L-'n p = hygepdf(0:5,100,20,10)
v kc(-n sFC1PdSk4T p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215
0}Kl47 }aD L L9I:^ 详细可参见：
riFE.; http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 kYPowM Sn7.KY S 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
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U0zlG] C Z TjlGU ` x = 0:5
?# ,\, p = hygepdf(x,100,20,10);
ir \ d8. plot(x,p,':k*')
