CODEWITHSUNDEEP
matlabmatlab-figuresymbolscolorbar
M.amir
M.amir

Reputation: 65

How to add marker/symbol to colorbar

I want to add a marker/special tick mark in my MATLAB colorbar. For example, lets say I have a colorbar scale from -2 to 3 and my critical value is -1.8, how can I add a marker of the value by symbol/marker?

enter image description here

Upvotes: 3

Views: 1680

Answers (3)

gnovice
gnovice

Reputation: 125874

One way to do this is to fetch the colorbar position, compute the location where you want your marker, and place an annotation object (like an arrow) there:

% Plot sample data, displaying color bar and getting its limits:

data = peaks();
imagesc(data);
hBar = colorbar();
cLimits = caxis();
hold on;

% Select and plot a point of interest:

point = [31 15];
value = data(point(1), point(2));
plot(point(2), point(1), 'r+');

% Compute location of color bar pointer and make annotation:

barPos = get(hBar, 'Position');
xArrow = barPos(1)+barPos(3)/2+[0.05 0];
yArrow = barPos(2)+barPos(4)*(value-cLimits(1))/diff(cLimits)+[0 0];
hArrow = annotation('textarrow', xArrow, yArrow, ...
                    'String', num2str(value, '%.2f'), 'Color', 'r');

enter image description here

If the figure is resized, the position of the annotation object may shift with respect to the color bar. One way to avoid this is to tweak the axes and color bar resize behavior with the following code:

axesPos = get(gca, 'Position');
set(hBar, 'Location', 'manual');
set(gca, 'Position', axesPos);

This should allow the annotation object to stay fixed to the proper spot over the color bar.

Upvotes: 4

EBH
EBH

Reputation: 10450

Here is yet another option - just add/change the tick label at the specific value:

MarkTxt = '<-Mark';
imagesc(rand(10)-2) % something to plot
colormap('jet')
CB = colorbar;

% in case you DON'T want the value to appear:
value = -1.8;
t = find(CB.Ticks==value);
if ~isempty(t)
    CB.TickLabels{t} = MarkTxt;
else
    [CB.Ticks,ord] = sort([CB.Ticks value],'ascend');
    t = CB.Ticks==value;
    CB.TickLabels{t} = MarkTxt;
end

%% OR - in case you want the value to appear:
value = -1.24;
t = find(CB.Ticks==value);
if ~isempty(t)
    CB.TickLabels{t} = [CB.TickLabels{t} MarkTxt];
else
    [CB.Ticks,ord] = sort([CB.Ticks value],'ascend');
    t = CB.Ticks==value;
    CB.TickLabels{t} = [CB.TickLabels{t} MarkTxt];
end

Without the value: CB mark

With the value: CB mark value

Upvotes: 5

Adriaan
Adriaan

Reputation: 18197

You can simply add text outside the plotting area and use that for your marker:

A = rand(15);
f=figure;
imagesc(A);
text(7,7,'X','Color','red') % Put a red X in the middle
text(17.5,size(A,1)*(1-A(7,7)),'<marker'); % Set a marker on the colour bar for the middle point
colorbar

Which results in:

enter image description here

I haven't found a way yet to plot a marker over the colour bar, as the colour bar is not one of the plot children which I can use in uistack for some reason.

Upvotes: 2

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