NAG FL Interface
e01shf (dim2_​scat_​shep_​eval)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{m}$ – Integer Input

2: $\mathbf{x}\left(\mathbf{m}\right)$ – Real (Kind=nag_wp) array Input

3: $\mathbf{y}\left(\mathbf{m}\right)$ – Real (Kind=nag_wp) array Input

4: $\mathbf{f}\left(\mathbf{m}\right)$ – Real (Kind=nag_wp) array Input

On entry: m, x, y and f must be the same values as were supplied in the preceding call to e01sgf.

5: $\mathbf{iq}\left(\mathbf{liq}\right)$ – Integer array Input

On entry: must be unchanged from the value returned from a previous call to e01sgf.

6: $\mathbf{liq}$ – Integer Input

On entry: the dimension of the array iq as declared in the (sub)program from which e01shf is called.

Constraint: $\mathbf{liq}\ge 2\times \mathbf{m}+1$.

7: $\mathbf{rq}\left(\mathbf{lrq}\right)$ – Real (Kind=nag_wp) array Input

On entry: must be unchanged from the value returned from a previous call to e01sgf.

8: $\mathbf{lrq}$ – Integer Input

On entry: the dimension of the array rq as declared in the (sub)program from which e01shf is called.

Constraint: $\mathbf{lrq}\ge 6\times \mathbf{m}+5$.

9: $\mathbf{n}$ – Integer Input

On entry: $n$, the number of evaluation points.

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

10: $\mathbf{u}\left(\mathbf{n}\right)$ – Real (Kind=nag_wp) array Input

11: $\mathbf{v}\left(\mathbf{n}\right)$ – Real (Kind=nag_wp) array Input

On entry: the evaluation points $\left(u_{\mathit{i}},v_{\mathit{i}}\right)$, for $\mathit{i}=1,2,\dots ,n$.

12: $\mathbf{q}\left(\mathbf{n}\right)$ – Real (Kind=nag_wp) array Output

On exit: the values of the interpolant at $\left(u_{\mathit{i}},v_{\mathit{i}}\right)$, for $\mathit{i}=1,2,\dots ,n$. If any of these evaluation points lie outside the region of definition of the interpolant the corresponding entries in q are set to the largest machine representable number (see x02alf), and e01shf returns with $\mathbf{ifail}=\mathbf{3}$.

13: $\mathbf{qx}\left(\mathbf{n}\right)$ – Real (Kind=nag_wp) array Output

14: $\mathbf{qy}\left(\mathbf{n}\right)$ – Real (Kind=nag_wp) array Output

On exit: the values of the partial derivatives of the interpolant $Q\left(x,y\right)$ at $\left(u_{\mathit{i}},v_{\mathit{i}}\right)$, for $\mathit{i}=1,2,\dots ,n$. If any of these evaluation points lie outside the region of definition of the interpolant, the corresponding entries in qx and qy are set to the largest machine representable number (see x02alf), and e01shf returns with $\mathbf{ifail}=\mathbf{3}$.

15: $\mathbf{ifail}$ – Integer Input/Output

On entry: ifail must be set to $0$, $-1$ or $1$ to set behaviour on detection of an error; these values have no effect when no error is detected.

A value of $0$ causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of $-1$ means that an error message is printed while a value of $1$ means that it is not.

If halting is not appropriate, the value $-1$ or $1$ is recommended. If message printing is undesirable, then the value $1$ is recommended. Otherwise, the value $0$ is recommended. When the value $-\mathbf{1}$ 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, liq is too small: $\mathbf{liq}=〈\mathit{\text{value}}〉$.

On entry, lrq is too small: $\mathbf{lrq}=〈\mathit{\text{value}}〉$.

On entry, $\mathbf{m}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{m}\ge 6$.

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

$\mathbf{ifail}=2$

On entry, values in iq appear to be invalid. Check that iq has not been corrupted between calls to e01sgf and e01shf.

On entry, values in rq appear to be invalid. Check that rq has not been corrupted between calls to e01sgf and e01shf.

$\mathbf{ifail}=3$

On entry, at least one evaluation point lies outside the region of definition of the interpolant. At such points the corresponding values in q and qx contain extrapolated approximations. Points should be evaluated one by one to identify extrapolated values.

$\mathbf{ifail}=-99$

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

See Section 7 in the Introduction to the NAG Library FL Interface for further information.

$\mathbf{ifail}=-399$

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

See Section 8 in the Introduction to the NAG Library FL Interface for further information.

$\mathbf{ifail}=-999$

Dynamic memory allocation failed.

See Section 9 in the Introduction to the NAG Library FL Interface for further information.

7 Accuracy

8 Parallelism and Performance

9 Further Comments

9.1 Internal Changes

10 Example