# Plotting two contourf plots on the same plot

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Elie Hatem on 20 Jun 2020
Answered: Long Hoang Van on 24 Sep 2021
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?
Elie Hatem
clear all;clc;
x=-pi:0.1:pi;
y=x;
[X,Y]=meshgrid(x,y);
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 on 21 Jun 2020

Elie Hatem on 21 Jun 2020
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

Long Hoang Van on 24 Sep 2021
clear all;clc;
x=-pi:0.1:pi;
y=x;
[X,Y]=meshgrid(x,y);
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

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