# Plotting chemical 2d reaction in different colors

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Ulan Kelesbekov on 22 Apr 2020
Answered: Ayush Gupta on 9 Jun 2020
WIlling to make an image of a 2D reaction of mixing the reagents "A+B=C".
On input have Matrix A and B, velocites, pressures, calculated Stoke's, solved for Pressure and velocities, obtainted moving reagents A B, then calculated C matrix from reaction.
So far came up to this (images 2 and 3, please disregard the first Image):
contourf(x,y,C',20,'k:');
contourf(x,y,A.'+B.',20,'k-');
Question is to how to combine images 2 and 3 with different colours to display output on a single image, i.e. e.g. Red for A, Blue for B and Green for C and white for background.
##### 2 CommentsShow NoneHide None
BALAJI KARTHEEK on 22 Apr 2020
use hold on command
Ulan Kelesbekov on 24 Apr 2020
Edited: Ulan Kelesbekov on 24 Apr 2020
does not work for image() and contour() funciton, it overwrites the previous.

darova on 24 Apr 2020
What about alpha? Try to set transparency to your object and then just plot them together
[X1,Y1,Z1] = peaks(20);
[X2,Y2] = meshgrid(1:10);
R2 = hypot(X2,Y2);
h1 = surf(X2,Y2,Y2);
h2 = surface(5+X1,5+Y1,Z1/10);
% set([h1 h2],'edgecolor','none')
alpha 0.5
zlim([-1 1])
axis vis3d
for i = 1:100
Z2 = sin(R2+i/10)./R2;
set(h1,'zdata',Z2)
set(h2,'zdata',Z1/10*(50-i)/100)
pause(.1)
end
##### 2 CommentsShow NoneHide None
Ulan Kelesbekov on 24 Apr 2020
alpha seems not to work for countourf, it is suggested to enter manually for flat plot :(
darova on 24 Apr 2020
try to manually change using handles
[x,y,z] = peaks;
z1 = 10*sin(2*hypot(x,y))./hypot(x,y);
[~,h1] = contourf(x,y,z);
hold on
[~,h2] = contourf(x,y,z1);
hold off
h11 = get(h1,'children');
h22 = get(h2,'children');
set(h11,'facealpha',0.5)
set(h22,'facealpha',0.5)

Ayush Gupta on 9 Jun 2020
This problem can be tackled using the following approach. Suppose contour1.jpg is the first contour and cntour2.jpg is the second contour, the images can be superimposed using the given piece of code:
figure1 = figure;
ax1 = axes('Parent',figure1);
ax2 = axes('Parent',figure1);
set(ax1,'Visible','off');
set(ax2,'Visible','off');
I = imshow(a,'Parent',ax2);
alpha = 0.5;
imshow('contour2.jpg','Parent',ax1);

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