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chiinv
Evaluates the inverse chi-squared distribution function.
Prototype
function chiinv ( p : numeric, df : numeric ) return_val : numeric
Arguments
pA multi-dimensional array or scalar value equal to the integral of the chi-square distribution. [0<p<1]
dfA multi-dimensional array of the same size as p equal to the degrees of freedom of the chi-square distribution. (0, +infinity)
Return value
A multi-dimensional array of the same size as p. The return value is double if p is double, and a float array otherwise.
Description
Evaluates the inverse chi-squared distribution function by calculating the upper integration of the non-central chi-square distribution. This gives the same answers as IMSL's chiin function.
See Also
cdfchi_x is identical to chiinv. It exists to provide consistency with the other CDF functions.
Examples
Example 1
begin p = 0.99 df = 2. x = chiinv (p,df) ; or cdfchi_x (p,df) print ("p="+p+" df="+df+" x="+x) df = 64. x = chiinv (p,df) ; or cdfchi_x (p,df) print ("p="+p+" df="+df+" x="+x) end
The result is:
(0) p=0.99 df=2 x= 9.21034 (0) p=0.99 df=64 x=93.2169