Removing points from meshgrid (mask)

Hey!

I'm trying to remove points from my mesh grid in order to get a graph similar to this one:

Basically I want to remove all the points below the line given in the code below by h1.

clear all; close all; clc           % clear variables, close plots, clear screen

%% Constants 

D = 60;                             % Ekman layer depth (m)
rho_0 = 1025;                       % density (kg/m^3)
f = 0.545/(10^4);                   % Coriolis parameter
c = (1+i)*pi/D;                     % c parameter
ug = 0;                             % zonal geostrophic wind speed
tau_x = 0;                          % x-component of wind shear stress
tau_y = 0.07;                       % y-component of wind shear stress
tau = tau_x + i*tau_y;              % complex wind shear stress
u0 = (1-i)*pi*tau/(rho_0*f*D);      % surface Ekman velocity in the deep ocean limit
hDmax = 2.5;                        % maximum h/D value

%% Bathymetry

h1 = @(x) -x/1000;                  % bathymetry profile function
x_grid = linspace(-200000,0,1000);  % linearly spaced grid for the horizontal coordinate (offshore distance, x)
z_grid = linspace(-100,0,1000);     % linearly spaced grid for the vertical coordinate (depth, z)
h = h1(x_grid);                     % vector with bathymetry

tmp = find(h/D>hDmax);              % reduce offshore grid
xindex = tmp(end);
h = h(xindex:end);
L = length(h);
N = length(z_grid);

zeta = pi*h/D;                      % vector with zeta function values

%% Horizontally-varying structure functions
 
alpha = (cosh(zeta).*cos(zeta)).^2 + (sinh(zeta).*sin(zeta)).^2;
 
S1 = cosh(zeta).*cos(zeta)./alpha;
S2 = sinh(zeta).*sin(zeta)./alpha;
T1 = cosh(zeta).*sinh(zeta)./alpha;
T2 = cos(zeta).*sin(zeta)./alpha;
 
%% Velocities, transport and stream function
 
vg = (2*pi*tau_y/(rho_0*f*D)).*(1-S1)./(T1-T2) - ug.*(T1+T2-2.*pi.*h./D)./(T1-T2);                                  % meridional geostrophic wind speed  
ugu = h*0 + ug;                                                                                                     % adjusting the size of the vector
ugc = complex(ugu,vg);                                                                                              % complex total geostrophic velocity 
Uek = abs(tau_y/(rho_0*f));                                                                                         % Ekman transport
 
psi = zeros(N,L);
psi = complex(psi,psi);

for jj=1:L
    for ii=1:N
        psi(ii,jj) = (1/c).*(u0.*(1-(cosh(c.*(z_grid(ii)+h(jj))))./(cosh(c.*h(jj)))) +...
        ugc(jj).*sinh(c.*z_grid(ii))./cosh(c.*h(jj)));
    end
end
psi = real(psi);                                                                                                     % real part of stream function
 
%% Plotting

X_grid = repmat(-h/D,[N 1]);
Z_grid = repmat(z_grid/D, [L 1]);
Z_grid = Z_grid'
Z = psi/Uek;
  
contour(X_grid,Z_grid,Z,'ShowText','on','LevelStep',0.1)

The figure produced at the moment is the following:

What can I do?

Answer 1

[darova]

Try this simple script

[X,Y] = meshgrid(1:20);
n = [1 -1];
n = n/norm(n);                  % normal of a line
dist = -7;                      %
D = n(1)*X + n(2)*Y + dist;
X(D>0) = nan;
Y(D>0) = nan;
surf(X,Y,X*0+1)

The result:

[António Lúcio]

Hey there, thanks for your input, but I was actually thinking a bit more generally than what you sketch in your answer. For instance, for tha graphs below, h is not given by any analytical formula. Just a set of values. How would I eliminate all the values below each h value for each x?

[darova]

Use inpolygon to detect points in red region. Then assign NaN