NAG Library Routine Document

E02JFF

1 Purpose

2 Specification

3 Description

4 References

5 Parameters

1:   NXEVAL – INTEGERInput

On entry: $n_x$, the number of values in the $x$ direction forming the mesh on which the spline is to be evaluated.

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

2:   NYEVAL – INTEGERInput

On entry: $n_y$, the number of values in the $y$ direction forming the mesh on which the spline is to be evaluated.

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

3:   XEVALM(NXEVAL) – REAL (KIND=nag_wp) arrayInput

On entry: the $\left(x_i\right)$ values forming the mesh on which the spline is to be evaluated.

Constraint: for all $i$, $\mathbf{XEVALM}\left(i\right)$ must lie inside, or on the boundary of, the spline's bounding box as determined by E02JDF.

4:   YEVALM(NYEVAL) – REAL (KIND=nag_wp) arrayInput

On entry: the $\left(y_j\right)$ values forming the mesh on which the spline is to be evaluated.

Constraint: for all $j$, $\mathbf{YEVALM}\left(j\right)$ must lie inside, or on the boundary of, the spline's bounding box as determined by E02JDF.

5:   COEFS($*$) – REAL (KIND=nag_wp) arrayInput

On entry: the computed spline coefficients COEFS as output from E02JDF.

6:   FEVALM(NXEVAL,NYEVAL) – REAL (KIND=nag_wp) arrayOutput

On exit: if $\mathbf{IFAIL}=\mathbf{0}$ on exit $\mathbf{FEVALM}\left(i,j\right)$ contains the computed spline value at $\left(x_i,y_j\right)$.

7:   IOPTS($*$) – INTEGER arrayCommunication Array

On entry: must be the same array IOPTS supplied in a previous call to E02JDF. The contents of the array must not have been modified either directly or indirectly, by a call to E02ZKF, between calls to E02JDF and E02JFF.

8:   OPTS($*$) – REAL (KIND=nag_wp) arrayCommunication Array

On entry: must be the same array OPTS supplied in a previous call to E02JDF. The contents of the array must not have been modified either directly or indirectly, by a call to E02ZKF, between calls to E02JDF and E02JFF.

9:   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

$\mathbf{IFAIL}=6$

On entry, $\mathbf{NXEVAL}=⟨\mathit{\text{value}}⟩$.
Constraint: $\mathbf{NXEVAL}\ge 1$.

$\mathbf{IFAIL}=7$

On entry, $\mathbf{NYEVAL}=⟨\mathit{\text{value}}⟩$.
Constraint: $\mathbf{NYEVAL}\ge 1$.

$\mathbf{IFAIL}=9$

Option arrays are not initialized or are corrupted.

$\mathbf{IFAIL}=10$

The fitting routine has not been called, or the array of coefficients has been corrupted.

$\mathbf{IFAIL}=13$

On entry, $\mathbf{XEVALM}\left(⟨\mathit{\text{value}}⟩\right)=⟨\mathit{\text{value}}⟩$ was outside the bounding box.
Constraint: $⟨\mathit{\text{value}}⟩\le \mathbf{XEVALM}\left(i\right)\le ⟨\mathit{\text{value}}⟩$ for all $i$.

$\mathbf{IFAIL}=14$

On entry, $\mathbf{YEVALM}\left(⟨\mathit{\text{value}}⟩\right)=⟨\mathit{\text{value}}⟩$ was outside the bounding box.
Constraint: $⟨\mathit{\text{value}}⟩\le \mathbf{YEVALM}\left(j\right)\le ⟨\mathit{\text{value}}⟩$ for all $j$.

$\mathbf{IFAIL}=-999$

Dynamic memory allocation failed.

7 Accuracy

8 Further Comments

9 Example