NAG Library Routine Document

E01EBF

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     $\mathrm{M}$ – INTEGERInput

On entry: $m$, the number of points to interpolate.

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

2:     $\mathrm{N}$ – INTEGERInput

On entry: $n$, the number of data points. N must be unchanged from the previous call of E01EAF.

Constraint: $\mathbf{N}\ge 3$.

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

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

On entry: the coordinates of the $\mathit{r}$th data point, $\left(x_r,y_r\right)$, for $\mathit{r}=1,2,\dots ,n$. X and Y must be unchanged from the previous call of E01EAF.

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

On entry: the function values $f_{\mathit{r}}$ at $\left(x_{\mathit{r}},y_{\mathit{r}}\right)$, for $\mathit{r}=1,2,\dots ,n$.

6:     $\mathrm{TRIANG}\left(7\times \mathbf{N}\right)$ – INTEGER arrayInput

On entry: the triangulation computed by the previous call of E01EAF. See Section 9 in E01EAF for details of how the triangulation used is encoded in TRIANG.

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

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

On entry: the coordinates $\left({\mathit{px}}_{\mathit{i}},{\mathit{py}}_{\mathit{i}}\right)$, for $\mathit{i}=1,2,\dots ,m$, at which interpolated function values are sought.

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

On exit: the interpolated values $F\left({\mathit{px}}_{\mathit{i}},{\mathit{py}}_{\mathit{i}}\right)$, for $\mathit{i}=1,2,\dots ,m$.

10:   $\mathrm{IFAIL}$ – 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, $\mathbf{N}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{N}\ge 3$.

$\mathbf{IFAIL}=2$

On entry, $\mathbf{M}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{M}\ge 1$.

$\mathbf{IFAIL}=3$

On entry, the triangulation information held in the array TRIANG does not specify a valid triangulation of the data points. TRIANG has been corrupted since the call to E01EAF.

$\mathbf{IFAIL}=4$

At least one evaluation point lies outside the nodal triangulation. For each such point the value returned in PF is that corresponding to a node on the closest boundary line segment.

$\mathbf{IFAIL}=-99$

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