Fading colors in contourf

I have some data to process and to do so, I'm using a contourf-function. I would like my plots to have the colors fading into eachother instead of having clear lines between zones. Anyone that can help me with this?

%Processing input
Data = importdata('NH3.txt').data;
Speed = importdata('Speed.txt').data;
[Y,Z] = meshgrid(unique(Data(:,2),'sorted'),flip(unique(Data(:,3),'sorted')));

NH3 = zeros(65); %pre-allocation
U = zeros(65); %pre-allocation
for r = 1:65
    for k = 1:65
        NH3(r,k) = Data(find(Data(:,2)== Y(k,k) & Data(:,3) == Z(r,r)), 4);
        U(r,k) = Speed(find(Speed(:,2)== Y(k,k) & Speed(:,3) == Z(r,r)), 4);
    end
end

%Plotting
subplot(1,2,1)
    contourf(Y, Z, NH3, 'Linecolor', 'none')
    colorbar
    title('NH_3 concentratie [kg/m³]')
    xlabel('y [m]')
    ylabel('z [m]')
subplot(1,2,2)
    contourf(Y, Z, U, 'Linecolor', 'none')
    colorbar
    title('Snelheid in x-component [m/s]')
    xlabel('y [m]')
    ylabel('z [m]')

Answer 1

[Chunru]

%Processing input
Data = importdata('NH3.txt').data;
Speed = importdata('Speed.txt').data;
yy = unique(Data(:,2),'sorted');
zz = flip(unique(Data(:,3),'sorted'));

[Y,Z] = meshgrid(unique(Data(:,2),'sorted'),flip(unique(Data(:,3),'sorted')));
NH3 = zeros(65); %pre-allocation
U = zeros(65); %pre-allocation
for r = 1:65
    for k = 1:65
        NH3(r,k) = Data(find(Data(:,2)== Y(k,k) & Data(:,3) == Z(r,r)), 4);
        U(r,k) = Speed(find(Speed(:,2)== Y(k,k) & Speed(:,3) == Z(r,r)), 4);
    end
end
%Plotting
subplot(1,2,1)
    imagesc(yy, zz, NH3); hold on
    contour(Y, Z, NH3, 'Linecolor', 'k')
    colorbar
    title('NH_3 concentratie [kg/m³]')
    xlabel('y [m]')
    ylabel('z [m]')
subplot(1,2,2)
    imagesc(yy, zz, U); hold on
    contour(Y, Z, U, 'Linecolor', 'k')
    colorbar
    title('Snelheid in x-component [m/s]')
    xlabel('y [m]')
    ylabel('z [m]')

[Xander Caerts]

Without the lines ('Linecolor', 'none' ), that gives me exactly what I was looking for. Thank you!

[DGM]

If you're after interpolated color with no lines, then you really don't need a contour plot at all. Just use pcolor().