Plotting two contourf plots on the same plot

Hello,

I am trying to plot two data matrices on the same plot. However, I do not know how to adjust the transparancy of one of the plots.

The code is shown below with the attached data of Z1 and Z2.

If I try to plot the on top of each other just like the code of figure (3), the data values of the Z1 will not fully be visible since the Z2 data will be on top of it.

Is there a way to adjust the transparency of the plotted Z2 data so that the the full Z1 data will be visible?

And, is there a possibility to change the color of each contourf plot?

Thank you for your time,

Elie Hatem

clear all;clc;

x=-pi:0.1:pi;
y=x;
[X,Y]=meshgrid(x,y);

load('motorization_data.mat','Z1','Z2')


figure(1)
contourf(X,Y,Z1,[0 0])

figure(2)
contourf(X,Y,Z2,[0 0])

figure(3)
contourf(X,Y,Z1,[0 0])
hold on
contourf(X,Y,Z2,[0 0])
hold off

[madhan ravi]

https://www.mathworks.com/help/matlab/ref/alpha.html

[Elie Hatem]

Thank you for your response.

If I try to run the code bellow I get the following error:

Error using alpha (line 68)

Wrong number of arguments

Error in untitled (line 8)

alpha(j,0.1)

Maybe alpha is not supported for contourf plots?

clear all;clc;
x=-pi:0.1:pi;
y=x;
[X,Y]=meshgrid(x,y);
load('motorization_data.mat','Z1','Z2')
figure(1)
j=contourf(X,Y,Z1,[0 0])
alpha(j,0.1)

[madhan ravi]

https://www.mathworks.com/matlabcentral/answers/60106-how-to-make-one-contour-transparent-in-contourf#answer_72640

[Elie Hatem]

Yes, I saw this link prior to asking my question.

I tried to use "fill". However, my plot was not plotting as desired.

I solved the problem by removing the columns which have zero elements in the X axis since it was clear that neither their X (which is zero) and their Y (belonging to the zero in the X) are part of the data. They were introduced when taking contourf was used. Moreover, the code below solved my problem:

figure(3)
j=contourf(X,Y,Z1,[0 0]);
hold on
contourf(X,Y,Z2,[0 0])
hold off

% Removing the unwanted values from j
i=0;
while (1)
    l_j=length(j);
    i=i+1;
    if i==143
        disp('i=143')
    end
    
    if j(1,i)==0
        j(:,i)=[];
        l_j=l_j-1;
    end
    
    if i==l_j
        break;
    end
end




%%
xi = j(1,:);
yi = j(2,:);

% Contour plot
figure(4)
contourf(X,Y,Z2,[0 0 ]);
% Transparent patch
hold on
fill(xi,yi,'m','FaceAlpha',0.5,'LineWidth',1);
hold off

[madhan ravi]

Post it as answer.

Answer 1

[Elie Hatem]

I solved the problem by removing the columns which have zero elements in the X axis since it was clear that neither their X (which is zero) and their Y (belonging to the zero in the X) are part of the data. They were introduced when taking contourf was used. Moreover, the code below solved my problem:

figure(3)
j=contourf(X,Y,Z1,[0 0]);
hold on
contourf(X,Y,Z2,[0 0])
hold off
% Removing the unwanted values from j
i=0;
while (1)
    l_j=length(j);
    i=i+1;
    if i==143
        disp('i=143')
    end
    
    if j(1,i)==0
        j(:,i)=[];
        l_j=l_j-1;
    end
    
    if i==l_j
        break;
    end
end
%%
xi = j(1,:);
yi = j(2,:);
% Contour plot
figure(4)
contourf(X,Y,Z2,[0 0 ]);
% Transparent patch
hold on
fill(xi,yi,'m','FaceAlpha',0.5,'LineWidth',1);
hold off

Answer 2

[Long Hoang Van]

clear all;clc;

x=-pi:0.1:pi;

y=x;

[X,Y]=meshgrid(x,y);

load('motorization_data.mat','Z1','Z2')

figure(1)

contourf(X,Y,Z1,[0 0])

figure(2)

contourf(X,Y,Z2,[0 0])

figure(3)

contourf(X,Y,Z1,[0 0])

hold on

contourf(X,Y,Z2,[0 0])

hold off