| 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 9_g>BI;"8
#
|[`1
ans = DQL06`pX/
yffU%
)
NaN b(+w.R(+Ti
AH"g^ gw~T
查看了一下帮助 help hygepdf I ,?Fqg'sq
G2U5[\
HYGEPDF Hypergeometric probability density function. n"K {uj))
+?4*,8Tmmz
Y = HYGEPDF(X,M,K,N) returns the hypergeometric probability ,f-T1v"
density function at X with integer parameters M, K, and N. o|b[(t$;O
Note: The density function is zero unless X is an integer. Res"0Q
9RCB$Ka6X
The size of Y is the common size of the input arguments. A scalar input ~@)- qV^~
functions as a constant matrix of the same size as the other inputs. nr<}Hc^f-
's56L,^:
See also hygecdf, hygeinv, hygernd, hygestat, pdf. m!FM+kge
0+VncL)u
Reference page in Help browser ~T;a jvJ
doc hygepdf #*ZnA,
6T}
CPDRq
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： < :kTTye|
)%H5iSNG$P
http://ccpublic-1.central.cranfield.ac.uk/2001DMSOMFRC/pr062320/Matlab/stats/hygepdf.m A ~yw8v5UF
i;uG:,ro
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_W9.u
E9 80yXJR
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?
_{F dw
J*^,l`C/
p = hygepdf(0:5,100,20,10) 32)&;
Qw{\sCH>
p = 0.0951 0.2679 0.3182 0.2092 0.0841 0.0215 rH#c:BwSm
Qzs\|KS
详细可参见： Jnu}{^ ~
http://www.physnet.uni-hamburg.de/physnet/matlab/help/toolbox/stats/hygepdf.html#4257 3^iQe"P%a@
-x3tx7%
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 J1u@A$4l?
dwf #~7h_
x = 0:5 8KGv?^M
6W
p = hygepdf(x,100,20,10); 1 o5Y9#7
plot(x,p,':k*')
|
|