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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 iX9[Q0g=oQ D=pI'5& ans = %l]rQjV- h>`'\qy NaN 7p"~:1hU 8zB+%mcF 查看了一下帮助 help hygepdf +'YSpJ C>(M+qXL+ HYGEPDF Hypergeometric probability density function. ,:Rq H?zCIue3 Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability O}\"$n> density function at X with integer parameters M, K, and N. Z:o'
+oh Note: The density function is zero unless X is an integer. %]= 'Uv^x VHXR)} The size of Y is the common size of the input arguments. A scalar input +XaO?F[c functions as a constant matrix of the same size as the other inputs. UdM5R
[ [7Kj$PB3 See also hygecdf, hygeinv, hygernd, hygestat, pdf. q}76aa0e xr7<(:d Reference page in Help browser "
:nVigw& doc hygepdf oT5rX
,8 5IF~]5s 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: y [7xK}`_ jJ{
w -$ http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m yKk,); b\uB 直到发现这个例子后才清楚各个参数所代表的具体意义。 URzE+8m^ M6 >\R$ 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? 9[]"%6 #lVl?F+~ p = hygepdf(0:5,100,20,10) #}]il0d J;]@?( p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215 Zo638*32 h/y} 详细可参见: KL_}:O68 http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 8@C|exAD` 2W-NCE%K)T 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 f`";Q/rG +M%2m3.Jo x = 0:5 kGTc~p( p = hygepdf(x,100,20,10); x jUH<LFxy plot(x,p,':k*')
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