How to make a line plot with a colorbar as the third variable?
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Hello community,
Lets say I have three variables, being Y the variable one. X and Z are constant, of which Y depends on.
x= linspace(0,100,500);
z= [5, 15, 25, 35];
(I won't show the whole equations, so I'm just going to leave a made up function to demonstrate how all the variables influence each other)
for i = 1:length(z)
K1 = konstant+ z(i);
y(i,:) = (K1.*x)./((1 + (K1.*x)));
end
As an amateur in coding (general), I've seen similarish examples, but not one that could resemble to what I'm looking foward, which is shown below:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/861225/image.png)
I know that is possible to apply the colormap function, but I'm having a bit of dificulties setting up the function, including the Ticks.
for i = 1:length(z)
color = z(i,:);
plot(x, y(i,:), 'color',color);
h = colorbar('Ticks',0:0.25:1,'TickLabels',{'5','15','25','35'});
Something like this? All help is appeciated. Thank you.
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Réponses (3)
Ty Watkins
le 12 Jan 2022
You need to set the 'color' for each corresponding z value based on the colormap.
Given the equations you provided in your questions (though I added a value for konstant and changed the line for K1 so the lines would actually show up on the plot) here is a simple solution.
konstant = 0.01;
x= linspace(0,100,500);
z= [5, 15, 25, 35];
for i = 1:length(z)
K1 = konstant * z(i);
y(i,:) = K1.*x ./ (1 + K1.*x);
end
figure();
hold on;
grid on;
box on;
cmap = colormap('winter'); % take your pick (doc colormap)
zmap = linspace( min(z), max(z), length(cmap));
for i = 1:length(z)
color = interp1( zmap, cmap, z(i));
plot(x, y(i,:), 'color',color);
end
caxis([min(z), max(z)])
colorbar()
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Ty Watkins
le 13 Jan 2022
Yes, that can just as easily be done by getting the color code from the colorbar for the Z value of each data point.
mcolor = interp1( zmap, cmap, ZVALUE);
And then you can use this RGB triplet to set either the 'markerfacecolor' or the 'markeredgecolor' in the plot command.
plot(xdata, ydata), '+', 'markerfacecolor', mcolor, 'markeredgecolor', mcolor);
If you have a set of ZVALUE's, the above code snippet will return the same size array of corresponding color values.
Bjorn Gustavsson
le 12 Jan 2022
When I want to plot colour-coded curves I use one of these functions from the file exchange:
They should give you something to either use as is or take as a template for how to do it.
HTH
Image Analyst
le 13 Jan 2022
You need to have a colormap that is an N-by-3 array, not like your z which is a 1-by-4 array. Try this:
% Initialization Steps.
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clear; % Erase all existing variables. Or clearvars if you want.
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 18;
x = linspace(0,100,500);
z = [5, 15, 25, 35]/1000;
konstant = 0.00005;
% Create a colormap with as many colors as elements in z.
Lz = length(z);
cMap = jet(Lz);
% Create y matrix.
y = zeros(Lz, length(x));
for k = 1 : Lz
K1 = konstant + z(k);
y(k, :) = (K1.*x) ./ ((1 + (K1.*x)));
end
% Plot the different y curves.
for k = 1 : Lz
thisColor = cMap(k,:);
plot(x, y(k,:), 'color',thisColor, 'LineWidth', 4);
hold on;
tickLabels{k} = sprintf('%g', 1000 * z(k));
end
miny = min(y(:))
maxy = max(y(:))
caxis([miny, maxy])
grid on;
xlabel('x', 'FontSize', fontSize);
ylabel('y', 'FontSize', fontSize);
colormap(cMap);
h = colorbar('Ticks', linspace(miny, maxy, Lz), 'TickLabels', tickLabels);
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/861990/image.png)
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