Describe a colormap in the legend of a plot

Question

Markus Reichel 2022-6-24

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1747610-describe-a-colormap-in-the-legend-of-a-plot

评论： Voss 2022-6-24

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 个评论
显示 2更早的评论隐藏 2更早的评论

Markus Reichel 2022-6-24

在 MATLAB Online 中打开

Don´t the Ticks just set the position for the TicksLabels? I want a TicksLabel on the red end, the middle where currently the value is displayed, and on the blue end. Not only in the middle like its´s currently displayed.

Also I found the problem with the labeling for the color bar.

colbar1.Label.String = 'Acceleration'; colbar1.Label.FontSize = 20; colbar1.Label.VerticalAlignment = 'top';

Now the label is on the right side of the bar. I tried using VerticalAlignment = 'bottom' but it will still display the label on the right hand side. Is there a way to show it on the left side of the color bar?

Markus Reichel 2022-6-24

在 MATLAB Online 中打开

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!

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Voss 2022-6-24

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1747610-describe-a-colormap-in-the-legend-of-a-plot#answer_992840

在 MATLAB Online 中打开

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');

2 个评论
显示无隐藏无

Markus Reichel 2022-6-24

Amazing! Thank you!!

Voss 2022-6-24

You're welcome!

请先登录，再进行评论。

Answer 2

John D'Errico 2022-6-24

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1747610-describe-a-colormap-in-the-legend-of-a-plot#answer_992790

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 个评论
显示 -1更早的评论隐藏 -1更早的评论

Markus Reichel 2022-6-24

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!

请先登录，再进行评论。