| 我是菜鸟 |
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 xB|?}uS-
cIO M}/gqv
ans = [` U9
&uLC{I k}
NaN }gtkO&
fBZR
查看了一下帮助 help hygepdf R}0xWPt9G
q %hxU.h
HYGEPDF Hypergeometric probability density function. TKrh3
xa?
Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability cwBf((~
density function at X with integer parameters M, K, and N. YdF\*tZ
Note: The density function is zero unless X is an integer. ]}A3Pm- t*
&\
\)x.!
The size of Y is the common size of the input arguments. A scalar input VhX~sJ1%Gp
functions as a constant matrix of the same size as the other inputs. C,G $C7$%
wJ> 2}
See also hygecdf, hygeinv, hygernd, hygestat, pdf. c~v(bK
egh_1Wg2a
Reference page in Help browser 3 fh lMOm
doc hygepdf -=VGXd
@DniYt /
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： Pj 7n_&*/
1%k$9[ !l%
http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m MtXTh*4
, Vr'F
直到发现这个例子后才清楚各个参数所代表的具体意义。 E;Q
,{{#
\Ss6F]K]
Suppose you have a lot of 100 floppy disks and you know that 20 of them are defective. What is the probability of drawing 0 through 5 defective floppy disks if you select 10 at random?
~[3B<^e
bqSp4TI
p = hygepdf(0:5,100,20,10) ?) mM]2%%
C
]+J
p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215 V^E.9fs,
\i M
详细可参见： zqs|~W]c
http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 Hribk[ 99
ht5eb"c+ 8
果然与一般对超几何分布公式字母惯常表示方式有所不同。尝试将上述分布作图如下 kzXmiBL<9
;nZN}&m
x = 0:5 L6f$I D:
p = hygepdf(x,100,20,10); mrId`<L5l{
plot(x,p,':k*')
|
|