selection of graph points

I have a code that builds level lines for my function of two variables, I need to leave out of these points only those for which the values of 'd' stand apart from each other at a distance of 4.04, i.e. we have a vector of values for points [tv,dv] and we leave in it only the points we need and we are building a schedule. How can this be implemented?

%% initial conditions
% global k0 h_bar ksi m E C_2
Ef = 2.77*10^3; 
Kb = physconst('boltzmann'); % 1.38*10^(-23)
m = 9.1093837*10^(-31);
Tc = 1.2;
ksi = 10^(-9);
h_bar = (1.0545726*10^(-34));
k0 = (ksi/h_bar)*sqrt(2.*m.*pi.*Kb.*Tc);
C_2 = 6.81;
t = linspace(0.1, 2,500);
D = linspace(2*10^(-9), 100*10^(-9),500);
d = D./ksi;
%d = linspace(2, 100,500);

%[TT,DD] = meshgrid(t,d);
%contour(TT, DD, @f_calc);
for i=1:numel(d)
    for j = 1:numel(t)
        F(i,j) = f_calc(t(j),d(i), k0, h_bar, ksi, m, C_2);
    end
end
%plot(t,F)
figure
[c,h] = contour(t,d,F,[0 0]);
xlabel('d') 
ylabel('t')

% tv = c(2, 2:end);
% dv = c(1, 2:end);
[tv,dv] = getContour0(c,h); 

Levels = 0

Q1 = [size(c); size(tv)]

Q1 = 2×2

2 13404 1 13389

figure
plot(dv, tv, mlbdt.VarName2, mlbdt.VarName1, 'ob');

Unable to resolve the name 'mlbdt.VarName2'.

%scatter(mlbdt.VarName2,mlbdt.VarName1, 'black');
xlabel('d')
ylabel('t')
grid
%mesh(t,d,F)
function F = f_calc(t, d, k0, h_bar, ksi, m, C_2) 
% global k0 h_bar ksi m C_2
%{
if 45 <= d && d <= 52
    nD = floor(375/(2*pi.*t*1.2) - 0.5)+1;
else
    nD = floor(375/(2*pi.*t*1.2) - 0.5);
end
%}
nD = floor(375/(2*pi.*t*1.2) - 0.5);
F = 0;
for k = 0:nD
    %F  = F + 1/(2*k+1).*(k0.*real(((f_p1(k,t)-f_p2(k,t))./2))+(f_arg_2(k,t,d,k0)-f_arg_1(k,t,d,k0))./d); 
    F = F + 1/(2*k+1).*imag(f_lg(k,t,d,k0)+1i.*d.*k0.*((f_p1(k,t)-f_p2(k,t))./2)+1i*f_arg_1(k,t,d,k0)-1i*f_arg_2(k,t,d,k0));
end
%F = -F - 6.81;
F = -(1/d).*F - 7.826922968141167;
end
function p1 = f_p1(n,t)
p1 = ((1+1i)./sqrt(2)).*sqrt(t.*(2.*n+1));
end
function p2 = f_p2(n,t)
p2 = sqrt(3601+1i.*t.*(2.*n+1));
end 
function arg_1 = f_arg_1(n,t,d,k0)
% global k0
arg_1 = angle(1+exp(-1i.*d*k0.*f_p1(n,t)));
end
function arg_2 = f_arg_2(n,t,d,k0)
% global k0
arg_2 = angle(1+exp(-1i.*d*k0.*f_p2(n,t)));
end
function n_lg = f_lg(n,t,d,k0)
%     global k0;
arg_of_lg = (1+exp(-1i.*d.*k0.*f_p1(n,t)))/(1+exp(-1i.*d.*k0.*f_p2(n,t)));
n_lg = log(abs(arg_of_lg));
end

function [xv,yv] = getContour0(M,C) % получение двух выходных значений от функции getContour0
Levels = C.LevelList 
for k = 1:numel(Levels)
    idx = find(M(1,:) == 0);
    ValidV = rem(M(2,idx),1) == 0;
    StartIdx{k,:} = idx(ValidV);
    VLen{k,:} = M(2,StartIdx{k});
    %         Q3 = numel(StartIdx{k})
    for k1 = 1:numel(StartIdx{k})
        %                 Q4 = StartIdx{k}(k1)
        idxv = StartIdx{k}(k1)+1 : StartIdx{k}(k1)+VLen{k}(k1);          % Index For Contour 'k1'
        xc{k1} = M(1,idxv);
        yc{k1} = M(2,idxv);
    end
end
xy = [cell2mat(xc); cell2mat(yc)].'; % .' обменивается индексом строки и столбца для каждого элемента. Транспонирование
xy = sortrows(xy,2);
xv = xy(:,1).'; 
yv = xy(:,2).';
%     figure
%     plot(xv, yv, '-r')
%     grid
%     title('Test Plot')
end