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2008-10-27 15:59 |
Matlab中超几何分布作图介绍
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 V4EM5 Z\k ]< +3Vw ans = 9N1#V
K yp?w3|`4; NaN =1/q)b,p) }1F6?do3& 查看了一下帮助 help hygepdf -nGwuEngP Ju4.@ HYGEPDF Hypergeometric probability density function. lvx]jd\ 5y}BCY2=/ Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability wn1,
EhHt density function at X with integer parameters M, K, and N. P>fKX2eQ- Note: The density function is zero unless X is an integer. (FG^UA#' ?DRR+n _ The size of Y is the common size of the input arguments. A scalar input (,U7 R^ functions as a constant matrix of the same size as the other inputs. ;b| UFIjW[h See also hygecdf, hygeinv, hygernd, hygestat, pdf. {!y<<u1 m\ ?\6Wk Reference page in Help browser *7_@7=W, doc hygepdf ]\`w1'* EP(Eq 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: 8J):\jAZ6 +nzTxpcP@K http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m ZBC@xM&- _{mJ.1)V; 直到发现这个例子后才清楚各个参数所代表的具体意义。 D$mf5G & QheDF7'z Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random? VRB~7\A5<) Gn[ *?=Vy p = hygepdf(0:5,100,20,10) %:%MUdl6 x*J|i4 p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215 ^F&A6{9f/h _)q4I(s* 详细可参见: ~Zu}M>-^c, http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 FTbtAlqh< 3r`<(%\ 果然与一般对超几何分布公式字母惯常表示方式有所不同。尝试将上述分布作图如下 6$DG.p k0knPDbHv x = 0:5 ^7<[}u;qF p = hygepdf(x,100,20,10); boIVU`F-! plot(x,p,':k*')
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