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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 <BdC#t:*L
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ans = idS+&:'
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NaN # M
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查看了一下帮助 help hygepdf 1P BnGQYM
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HYGEPDF Hypergeometric probability density function. [2
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Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability Z#GR)jb+
density function at X with integer parameters M, K, and N. R^K:hKQ
Note: The density function is zero unless X is an integer. k6;pi=sYNW
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The size of Y is the common size of the input arguments. A scalar input |g\CS 4$
functions as a constant matrix of the same size as the other inputs. a=[|"J<M
nxuR^6 Ai
See also hygecdf, hygeinv, hygernd, hygestat, pdf. E/d\ebX|
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Reference page in Help browser |A H@W#7j
doc hygepdf (<|1/ ^~=
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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： n8&x=Z}Xs
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http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m od3b, Q
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直到发现这个例子后才清楚各个参数所代表的具体意义。 ^687U,+
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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? Tz/[P:O3
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p = hygepdf(0:5,100,20,10) 1a#R7chl
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p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215 wY7+E/
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详细可参见： b$B-LvHd1
http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 :*Z@UY
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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 :-b-)*TC;
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x = 0:5 2- wgbC5
p = hygepdf(x,100,20,10); 35SL*zS@-
plot(x,p,':k*')
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