Overlaying gradient patches in single plot.

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I have created two gradient patches: the colormap for one goes from red to white (i.e., [1,0,0] --> [1, 1, 1]) over the range [1000,1600] along the x-axis of a subplot, while the other colormap goes from white to blue (i.e., [1, 1, 1] --> [0, 0, 1]/) over the range [1400, 2000] along the x-axis of a second subplot. xlim for both suplots is [1000, 2000], and I use a for loop with 256 iterations to create the colormaps. Is there any way to superimpose the two patches in one x-y plot (adjusting transparency so that both gradients are visible where the colored portions of the two patches overlap (i.e., x = 1400 --> 1600)? Thanks in advance.

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Eric 2021-6-1

在 MATLAB Online 中打开

function varargout = Tamb_vs_Altitude_gradient()
clc; close all;
x_lo = [1000 ; 1000; 1600; 1600];   %   x-limits for RED gradient
x_hi = [1400 ; 1400; 2000; 2000];   %   x-limits for BLUE gradient
y = [0; 500; 500; 0];   % y-limits for BOTH gradients 
c = [0; 0; 1; 1];
num_steps = 256;
for cm = 1:num_steps    % Create the colormaps
    Ag_colormap_lo(cm,:) = [255, 0 + cm*(255-0)/num_steps, 0 + cm*(255-0)/num_steps]/255;
    Ag_colormap_hi(cm,:) = [255 - cm*(255-0)/num_steps, 255 - cm*(255-0)/num_steps, 255]/255;
end
save('Tamb_gradient_colormap.mat','Ag_colormap_lo','Ag_colormap_hi');
figure();
ax(1) = subplot(2,1,1);     % Plot the RED gradient
p_lo = patch(x_lo,y,c); 
   set(p_lo,'FaceAlpha',1)  % Adjust transparency of RED gradient
shading interp;
colorbar;
xlim([1000 2000]); ylim([0 500]);
ax(2) = subplot(2,1,2);     % Plot the BLUE gradient
p_hi = patch(x_hi,y,c); 
   set(p_hi,'FaceAlpha',1)  % Adjust transparency of BLUE gradient
shading interp;
colorbar;
xlim([1000 2000]); ylim([0 500]);
colormap(ax(1),Ag_colormap_lo);     % Assign RED colormap to RED gradient
colormap(ax(2),Ag_colormap_hi);     % Assign BLUE colormap to BLUE gradient
end
%%

Eric 2021-6-1

gradient_superposition.pdf

Here're the gradients I wish to superimpose on the one axis.

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Answer 1

darova 2021-6-5

编辑：darova 2021-6-5

在 MATLAB Online 中打开

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See this

% x_lo = [1000 ; 1000; 1600; 1600]; % x-limits for RED gradient

% x_hi = [1400 ; 1400; 2000; 2000]; % x-limits for BLUE gradient

% y = [0; 500; 500; 0]; % y-limits for BOTH gradients

num_steps = 10;

x = [linspace(1000,1400,num_steps) linspace(1600,2000,num_steps)]; % x coord

X = [x;x]; % the same top and bottom

Y = [0*x;0*x+500]; % Y coord

c = linspace(0,1,num_steps); % color interpolatioon

red = interp1([0 1],[1 0 0;1 1 1],c); % create red chanel

blu = interp1([0 1],[1 1 1;0 0 1],c); % create blue chanel

C = reshape([red;blu],1,[],3); % 3D matrix of colors

C = [C;C]; % the same top and bottom

surf(X,Y,X*0,C)

view(0,90)

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Eric 2021-6-5

Hello, Darova -

That's good stuff, but not quite what I was hoping would be possible, which would be the two gradients overlapping in the range of x = [1400 1600], producing a 'zone' that would go from red (RGB = [255, 0, 0] near 1400) to blue (RGB = [0, 0, 255] near 1600), and progressing from red through various shades of violet in between.

However, THANKS TO YOUR ANSWER, I learned enough to be able to produce exactly what I wanted. Couldn't have done it without your help. A gazillion thanks to you!!!

Eric

darova 2021-6-5

You are welcome

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Overlaying gradient patches in single plot.

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