g01ecf

Purpose

Synopsis

[fun_value,ifail] = g01ecf(tail,x,df<,ifail>)

Description

 
                                         2                       
 The lower tail probability for the (chi)  distribution with (nu) 
 degrees of freedom, P(X<=x:(nu)) is defined by:
 
 
                                      x                
                         1            /   (nu)/2-1 -X/2
 P(X<=x:(nu))= ---------------------- |  X        e    dX,
                (nu)/2                /                
               2      (Gamma)((nu)/2) 0.0              
 
                                                     x>=0,(nu)>0.
 

Parameters

g01ecf

Required Input Arguments:

tail (1)                              string
x                                     real
df                                    real

Optional Input Arguments:                       <Default>

ifail                                 integer  -1

Output Arguments:

ifail                                 integer