# Interpolating over a grid

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Christian Mathiesen on 7 Nov 2021
Hello. I have a grid of x and y coordinates and I would like to interpolate some z values over this grid. The grid constitues an area of ocean, and the z values, d_sea, constitutes sea depth values in metres. The dataset seadepth_002536 is a line of known seadepth values. I would like to know the sea depth values of the entire [x,y] grid. I have tried using interp2 but I am getting errors. Any help is appreciated. Thanks.
v_sea = 1500; %p-wave velocity of water
v_sed = 2000; %p-wave velocity of sediment
x = tykkelse_002536(:,1);
y = tykkelse_002536(:,2);
d = tykkelse_002536(:,3);
d = d .* v_sed;
[Uxz_sea,ia,ic] = unique([x_sea d_sea],'rows');
x_sea = Uxz_sea(:,1);
d_sea = Uxz_sea(:,2);
d_sea = d_sea .* v_sea;
dx = 20;
x_ax=min(x):dx:max(x);
y_ax=min(y):dx:max(y);
[xx,yy]=meshgrid(x_ax,y_ax);
zii = interp2(x_sea,y_sea,d_sea,xx,yy);
Error using griddedInterpolant
Interpolation requires at least two sample points for each grid dimension.

Error in interp2>makegriddedinterp (line 226)
F = griddedInterpolant(varargin{:});

Error in interp2 (line 126)
F = makegriddedinterp({X, Y}, V, method,extrap);

Chunru on 7 Nov 2021
v_sea = 1500; %p-wave velocity of water
v_sed = 2000; %p-wave velocity of sediment
x = tykkelse_002536(:,1);
y = tykkelse_002536(:,2);
d = tykkelse_002536(:,3);
d = d .* v_sed;
[Uxz_sea,ia,ic] = unique([x_sea d_sea],'rows');
x_sea = Uxz_sea(:,1);
d_sea = Uxz_sea(:,2);
d_sea = d_sea .* v_sea;
dx = 20;
x_ax=min(x):dx:max(x);
y_ax=min(y):dx:max(y);
[xx,yy]=meshgrid(x_ax,y_ax);
% zii = interp2(x_sea,y_sea,d_sea,xx,yy);
f = scatteredInterpolant(x_sea, y_sea, d_sea);
zii = f(xx, yy);
Christian Mathiesen on 7 Nov 2021
Excellent. Thanks a lot!

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