NAG Toolbox: nag_interp_2d_scat_shep_eval (e01sh)

Purpose

Syntax

Description

References

Parameters

Compulsory Input Parameters

1:     $\mathrm{x}\left(\mathbf{m}\right)$ – double array

2:     $\mathrm{y}\left(\mathbf{m}\right)$ – double array

3:     $\mathrm{f}\left(\mathbf{m}\right)$ – double array

m, x, y and f must be the same values as were supplied in the preceding call to nag_interp_2d_scat_shep (e01sg).

4:     $\mathrm{iq}\left(\mathit{liq}\right)$ – int64int32nag_int array

liq, the dimension of the array, must satisfy the constraint $\mathit{liq}\ge 2\times \mathbf{m}+1$.

Must be unchanged from the value returned from a previous call to nag_interp_2d_scat_shep (e01sg).

5:     $\mathrm{rq}\left(\mathit{lrq}\right)$ – double array

lrq, the dimension of the array, must satisfy the constraint $\mathit{lrq}\ge 6\times \mathbf{m}+5$.

Must be unchanged from the value returned from a previous call to nag_interp_2d_scat_shep (e01sg).

6:     $\mathrm{u}\left(\mathbf{n}\right)$ – double array

7:     $\mathrm{v}\left(\mathbf{n}\right)$ – double array

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

Optional Input Parameters

1:     $\mathrm{m}$ – int64int32nag_int scalar

Default: the dimension of the arrays x, y, f. (An error is raised if these dimensions are not equal.)

m, x, y and f must be the same values as were supplied in the preceding call to nag_interp_2d_scat_shep (e01sg).

2:     $\mathrm{n}$ – int64int32nag_int scalar

Default: the dimension of the arrays u, v. (An error is raised if these dimensions are not equal.)

$n$, the number of evaluation points.

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

Output Parameters

1:     $\mathrm{q}\left(\mathbf{n}\right)$ – double array

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 nag_machine_real_largest (x02al)), and nag_interp_2d_scat_shep_eval (e01sh) returns with $\mathbf{ifail}=\mathbf{3}$.

2:     $\mathrm{qx}\left(\mathbf{n}\right)$ – double array

3:     $\mathrm{qy}\left(\mathbf{n}\right)$ – double array

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 nag_machine_real_largest (x02al)), and nag_interp_2d_scat_shep_eval (e01sh) returns with $\mathbf{ifail}=\mathbf{3}$.

4:     $\mathrm{ifail}$ – int64int32nag_int scalar

$\mathbf{ifail}=\mathbf{0}$ unless the function detects an error (see Error Indicators and Warnings).

Error Indicators and Warnings

Cases prefixed with W are classified as warnings and do not generate an error of type NAG:error_n. See nag_issue_warnings.

   $\mathbf{ifail}=1$

On entry,	$\mathbf{m}<6$,
or	$\mathit{liq}<2\times \mathbf{m}+1$,
or	$\mathit{lrq}<6\times \mathbf{m}+5$,
or	$\mathbf{n}<1$.

   $\mathbf{ifail}=2$

Values supplied in iq or rq appear to be invalid. Check that these arrays have not been corrupted between the calls to nag_interp_2d_scat_shep (e01sg) and nag_interp_2d_scat_shep_eval (e01sh).

W  $\mathbf{ifail}=3$

At least one evaluation point lies outside the region of definition of the interpolant. At all such points the corresponding values in q, qx and qy have been set to the largest machine representable number (see nag_machine_real_largest (x02al)).

   $\mathbf{ifail}=-99$

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

   $\mathbf{ifail}=-399$

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

   $\mathbf{ifail}=-999$

Dynamic memory allocation failed.

Accuracy

Further Comments

Example

Open in the MATLAB editor: e01sh_example

function e01sh_example


fprintf('e01sh example results\n\n');

% Scattered Grid Data
x = [11.16; 12.85; 19.85; 19.72; 15.91;  0.00; 20.87;  3.45; 14.26; ...
     17.43; 22.80;  7.58; 25.00;  0.00;  9.66;  5.22; 17.25; 25.00; ...
     12.13; 22.23; 11.52; 15.20;  7.54; 17.32;  2.14;  0.51; 22.69; ...
      5.47; 21.67;  3.31];
y = [ 1.24;  3.06; 10.72;  1.39;  7.74; 20.00; 20.00; 12.78; 17.87; ...
      3.46; 12.39;  1.98; 11.87;  0.00; 20.00; 14.66; 19.57;  3.87; ...
     10.79;  6.21;  8.53;  0.00; 10.69; 13.78; 15.03;  8.37; 19.63; ...
     17.13; 14.36; 0.33];
f = [22.15; 22.11;  7.97; 16.83; 15.30; 34.60;  5.74; 41.24; 10.74; ...
     18.60;  5.47; 29.87;  4.40; 58.20;  4.73; 40.36;  6.43;  8.74; ...
     13.71; 10.25; 15.74; 21.60; 19.31; 12.11; 53.10; 49.43;  3.25; ...
     28.63;  5.52; 44.08];

% Generate interpolant
nw = int64(0);
nq = int64(0);
[iq, rq, ifail] = e01sg(x, y, f, nw, nq);

% Interpolation points
u = [20.00;  6.41;  7.54;  9.91; 12.30];
v = [ 3.14; 15.44; 10.69; 18.27;  9.22];

% Interpolate at interpolation points 
[q, qx, qy, ifail] = e01sh(x, y, f, iq, rq, u, v);

fprintf('Interpolated values Q and its derivatives at (u,v)\n'); 
fprintf('     u      v      q      qx     qy\n');
for i = 1:size(u,1)
  fprintf('%7.2f%7.2f%7.2f%7.2f%7.2f\n', u(i), v(i), q(i), qx(i), qy(i));
end

e01sh example results

Interpolated values Q and its derivatives at (u,v)
     u      v      q      qx     qy
  20.00   3.14  15.89  -1.28  -0.63
   6.41  15.44  34.05  -3.62  -3.56
   7.54  10.69  19.31  -2.84   0.81
   9.91  18.27  13.68  -1.59  -4.71
  12.30   9.22  14.56  -0.68  -0.78