NAG CL Interface
g01fcc (inv_​cdf_​chisq)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{p}$ – double Input

On entry: $p$, the lower tail probability from the required ${\chi }^2$-distribution.

Constraint: $0.0\le \mathbf{p}<1.0$.

2: $\mathbf{df}$ – double Input

On entry: $\nu$, the degrees of freedom of the ${\chi }^2$-distribution.

Constraint: $\mathbf{df}>0.0$.

3: $\mathbf{fail}$ – NagError * Input/Output

The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).

6 Error Indicators and Warnings

On any of the error conditions listed below except $\mathbf{fail}\mathbf{.}\mathbf{code}=$ NE_ALG_NOT_CONV g01fcc returns $0.0$.

NE_ALG_NOT_CONV

The algorithm has failed to converge in $〈\mathit{\text{value}}〉$ iterations. The result should be a reasonable approximation.

NE_ALLOC_FAIL

Dynamic memory allocation failed.
See Section 3.1.2 in the Introduction to the NAG Library CL Interface for further information.

NE_GAM_NOT_CONV

The series used to calculate the gamma function has failed to converge. This is an unlikely error exit.

NE_INTERNAL_ERROR

An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
See Section 7.5 in the Introduction to the NAG Library CL Interface for further information.

NE_NO_LICENCE

Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library CL Interface for further information.

NE_PROBAB_CLOSE_TO_TAIL

The probability is too close to $0.0$ or $1.0$.

NE_REAL_ARG_GE

On entry, $\mathbf{p}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{p}<1.0$.

NE_REAL_ARG_LE

On entry, $\mathbf{df}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{df}>0.0$.

NE_REAL_ARG_LT

On entry, $\mathbf{p}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{p}\ge 0.0$.

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example

10.1 Program Text

10.2 Program Data

10.3 Program Results