Describe a colormap in the legend of a plot

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I am plotting a spacecraft trajectory and use a colormap to visualize the acceleration Vector of the spacecraft in the first part of the trajectory.
The code looks like follow:
%setting color map for Acceleration Vector
Acc_min = floor(min(ab(ab>0))*10000000);
Acc_max = ceil(max(ab(ab>0))*10000000);
Acc_min = min(Acc_min,[],'all');
Acc_max = max(Acc_max,[],'all');
Delta_Acc = Acc_max - Acc_min;
Acc_vals = ceil(Delta_Acc);
cmap = colormap(jet(Acc_vals)); % colormap should be 'parula' or 'jet'
colval = round(abs(nor)*10000000-Acc_min); % number of different temperature color values
for i=1:nval
if colval(i) < 1
colval(i) = 1;
elseif colval(i) > Acc_vals
colval(i) = Acc_vals;
end
end
% plot accelearation vector
for i=1:2:nval-1
Acc_col = cmap(colval(i),:);
quiver3(pos(i,1),pos(i,2),pos(i,3),arrowlength*Acc(i,1),arrowlength*Acc(i,2),arrowlength*Acc(i,3),'Color', Acc_col)
end
Now I would like to describe the color map in the legend of the of the plot. I imagine a bar with the same color range and underneath, the actual acceleration values, for example 0.2 m/s^2 on the red end and 0.05 m/s^2 on the blue end. This is just an idea and any other recommendations how to properly label this are welcome!
Any help would be much appreciated!
  4 Comments
Markus Reichel
Markus Reichel on 24 Jun 2022
You were right. the Ticks values were not within the caxis.
With these values it´s working but I don´t know why:
colbar1.Ticks = linspace(-0.0061, 0.0061, 3) ;
Do you know how I can shift the label of the colorbar from the right to the left?
And thank you very much for your help!

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Accepted Answer

Voss
Voss on 24 Jun 2022
values = 1000*rand(10);
surface(1:10,1:10,values,'FaceColor','interp')
box on
grid on
view(3);
min_max = [min(values(:)) max(values(:))];
cmap = get(gca(),'Colormap');
n_colors = size(cmap,1);
legend_ax = axes(gcf(), ...
'Units','normalized', ...
'Position',[0.69 0.89 0.3 0.1], ...
'Box','on', ...
'Layer','top', ...
'XTick',[], ...
'YTick',[], ...
'XLim',[0 1], ...
'YLim',[0 2], ...
'YDir','reverse');
surface(legend_ax, ...
linspace(0,1,n_colors+1), ...
[0 1], ...
[0:n_colors; 0:n_colors], ...
'EdgeColor','none');
t = [ ...
text(legend_ax,[0 1],[1 1],sprintfc('%.2f',min_max)); ...
text(legend_ax,0.5,1,'m/s^2') ...
];
set(t(1),'HorizontalAlignment','left');
set(t(2),'HorizontalAlignment','right');
set(t(3),'HorizontalAlignment','center');
set(t,'VerticalAlignment','top');

More Answers (1)

John D'Errico
John D'Errico on 24 Jun 2022
Hard to put it into a legend, since legend is not designed to do that. Far easier (one line of code) to just put a title above the plot. Have it say something like "red = x (m/s^2) , blue = y (m/s^2)", where x and y are numbers of your choosing. Why make extra work for yourself when there is no gain?
  1 Comment
Markus Reichel
Markus Reichel on 24 Jun 2022
I would like to visualize this information for better interpretation. I now use colorbar() but have some problems with the labeling.
But thanks for the input!

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