NAG Library Routine Document

E01BFF

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     $\mathrm{N}$ – INTEGERInput

2:     $\mathrm{X}\left(\mathbf{N}\right)$ – REAL (KIND=nag_wp) arrayInput

3:     $\mathrm{F}\left(\mathbf{N}\right)$ – REAL (KIND=nag_wp) arrayInput

4:     $\mathrm{D}\left(\mathbf{N}\right)$ – REAL (KIND=nag_wp) arrayInput

On entry: N, X, F and D must be unchanged from the previous call of E01BEF.

5:     $\mathrm{M}$ – INTEGERInput

On entry: $m$, the number of points at which the interpolant is to be evaluated.

Constraint: $\mathbf{M}\ge 1$.

6:     $\mathrm{PX}\left(\mathbf{M}\right)$ – REAL (KIND=nag_wp) arrayInput

On entry: the $m$ values of $x$ at which the interpolant is to be evaluated.

7:     $\mathrm{PF}\left(\mathbf{M}\right)$ – REAL (KIND=nag_wp) arrayOutput

On exit: $\mathbf{PF}\left(\mathit{i}\right)$ contains the value of the interpolant evaluated at the point $\mathbf{PX}\left(\mathit{i}\right)$, for $\mathit{i}=1,2,\dots ,m$.

8:     $\mathrm{IFAIL}$ – INTEGERInput/Output

On entry: IFAIL must be set to $0$, $-1\text{ or }1$. If you are unfamiliar with this parameter you should refer to Section 3.3 in the Essential Introduction for details.

For environments where it might be inappropriate to halt program execution when an error is detected, the value $-1\text{ or }1$ is recommended. If the output of error messages is undesirable, then the value $1$ is recommended. Otherwise, if you are not familiar with this parameter, the recommended value is $0$. When the value $-\mathbf{1}\text{ or }\mathbf{1}$ is used it is essential to test the value of IFAIL on exit.

On exit: $\mathbf{IFAIL}=\mathbf{0}$ unless the routine detects an error or a warning has been flagged (see Section 6).

6  Error Indicators and Warnings

$\mathbf{IFAIL}=1$

On entry,

$\mathbf{N}<2$.

$\mathbf{IFAIL}=2$

The values of $\mathbf{X}\left(\mathit{r}\right)$, for $\mathit{r}=1,2,\dots ,\mathbf{N}$, are not in strictly increasing order.

$\mathbf{IFAIL}=3$

On entry,

$\mathbf{M}<1$.

$\mathbf{IFAIL}=4$

At least one of the points $\mathbf{PX}\left(\mathit{i}\right)$, for $\mathit{i}=1,2,\dots ,\mathbf{M}$, lies outside the interval [$\mathbf{X}\left(1\right),\mathbf{X}\left(\mathbf{N}\right)$], and extrapolation was performed at all such points. Values computed at such points may be very unreliable.

$\mathbf{IFAIL}=-99$

An unexpected error has been triggered by this routine. Please contact NAG.

See Section 3.8 in the Essential Introduction for further information.

$\mathbf{IFAIL}=-399$

Your licence key may have expired or may not have been installed correctly.

See Section 3.7 in the Essential Introduction for further information.

$\mathbf{IFAIL}=-999$

Dynamic memory allocation failed.

See Section 3.6 in the Essential Introduction for further information.

7  Accuracy

8  Parallelism and Performance

9  Further Comments

10  Example

10.1  Program Text

Program Text (e01bffe.f90)

10.2  Program Data

Program Data (e01bffe.d)

10.3  Program Results

Program Results (e01bffe.r)