stats_cdf_beta

(PECL stats >= 1.0.0)

stats_cdf_beta — Calculates any one parameter of the beta distribution given values for the others

说明

stats_cdf_beta ( float $par1 , float $par2 , float $par3 , int $which ) : float

Returns the cumulative distribution function, its inverse, or one of its parameters, of the beta distribution. The kind of the return value and parameters (par1, par2, and par3) are determined by which.

The following table lists the return value and parameters by which. CDF, x, alpha, and beta denotes cumulative distribution function, the value of the random variable, and shape parameters of the beta distribution, respectively.

Return value and parameters
which Return value par1 par2 par3
1 CDF x alpha beta
2 x CDF alpha beta
3 alpha x CDF beta
4 beta x CDF alpha

参数

par1

The first parameter

par2

The second parameter

par3

The third parameter

which

The flag to determine what to be calculated

返回值

Returns CDF, x, alpha, or beta, determined by which.

User Contributed Notes

n15m0_jk 21-Sep-2016 08:23
Decided to dive into the source code and provide a simple explanation:

Parameters:
int $which - Select which parameter to use in the CDF Binomial calculation, based on what the prior 3 parameters are.

where $which is 4:
$arg1 = p
$arg2 = sn
$arg3 = xn
returns pr

$which = 3
$arg1 = p
$arg2 = sn
$arg3 = pr
returns xn

$which = 2
$arg1 = p
$arg2 = xn
$arg3 = pr
returns sn

$which = 1
$arg1 = sn
$arg2 = xn
$arg3 = pr
returns p
Anonymous 30-Dec-2009 12:29
Additional Notes, taken from source.
 WHICH --> Integer indicating which of the next four argument
       values is to be calculated from the others.
     Legal range: 1..4
     iwhich = 1 : Calculate P and Q from X,Y,A and B
     iwhich = 2 : Calculate X and Y from P,Q,A and B
     iwhich = 3 : Calculate A from P,Q,X,Y and B
     iwhich = 4 : Calculate B from P,Q,X,Y and A
    
     P <--> The integral from 0 to X of the chi-square
     distribution.
     Input range: [0, 1].
    
     Q <--> 1-P.
     Input range: [0, 1].
     P + Q = 1.0.
    
     X <--> Upper limit of integration of beta density.
     Input range: [0,1].
     Search range: [0,1]
    
     Y <--> 1-X.
     Input range: [0,1].
     Search range: [0,1]
     X + Y = 1.0.
    
     A <--> The first parameter of the beta density.
     Input range: (0, +infinity).
     Search range: [1D-100,1D100]
    
     B <--> The second parameter of the beta density.
     Input range: (0, +infinity).
     Search range: [1D-100,1D100]