Labelling the concentric circles

Hi there. My aim is to plot multiple concentric circles at different locations on a picture. The following coding was used to accomplish it. My problem is I want to label each circle with a value on the legend. So each circle will have different colour and the legend will show the value. It would be better if i could label it on the cirlce itself. I tried to do it with the legend command, but it didn't work. Can anyone help me out? Thank you.

The coding are as follows:

I = imread('aaaa.png') ;

figure(1)

imshow(I)

th = linspace(0,2*pi) ;

hold all

while true

hold all

message = sprintf('Click where you want the center to be');

uiwait(helpdlg(message));

[xCenter, yCenter] = ginput(1);

X=[5,30,100];

for radius =(X)

x = radius * cos(th) + xCenter;

y = radius * sin(th) + yCenter;

plot(x, y, '-');

title('Risk Contour')

end

legend(input('array form'),'AutoUpdate','off')

hold all

j = input(' Stop and proceed? (input: "y" - yes (stop) or "n" - no (if want to plot another contour))\n','s');

if j=='n'

continue

elseif j=='y'

break

else

disp('Error:Input should be ''y'' or ''n''\n')

end

end

Answer 1

[Suraj Kumar]

Hi HAINGKHARRAN ,

To accomplish your requirement of plotting multiple concentric circles at different locations and editing the labels manually , I made a few modifications to your code:

1. Hold on is used instead of hold all as it is deprecated.
2. The user is now provided with graphical dialog box instead using the command line for confirmation.
3. Ability to manually edit the label of the circles is added. To achieve the functionality of editing the label of each circle manually, you can use a callback function which will helps to edit the text by allowing user to input the label in a dialog box.

You can refer to the following code snippet-:

I = imread('aaaa.png'); 
figure(1)
imshow(I) 
th = linspace(0, 2*pi);   
hold on 

while true 
    message = sprintf('Click where you want the center to be'); 
    uiwait(helpdlg(message)); 
    [xCenter, yCenter] = ginput(1); 
    % Check if the user pressed "Enter" without clicking 
    if isempty(xCenter) 
        break; 
    end 
    X = [5, 30, 100]; % Radius of the concentric circles defined 
    for radius = X 
        x = radius * cos(th) + xCenter; 
        y = radius * sin(th) + yCenter; 
        h = plot(x, y, '-'); 
        title('Risk Contour') 
        % Label the circle with its radius and make the label editable 
        labelStr = sprintf('%.2f', radius); 
        textHandle = text(xCenter, yCenter - radius, labelStr, ... 
                          'Color', h.Color, ... 
                          'VerticalAlignment', 'bottom', ... 
                          'HorizontalAlignment', 'center', ... 
                          'BackgroundColor', 'w', ... 
                          'Margin', 1, ... 
                          'FontWeight', 'bold', ... 
                          'ButtonDownFcn', @editText); % Add callback for editing 
        end 
     % Ask the user if they want to continue or stop 
choice = questdlg('Do you want to plot another contour?', ... 

                      'Continue', 'Yes', 'No', 'Yes'); 
if strcmp(choice, 'No') 
        break; 
    end 
end 
% Callback function for editing text labels 
function editText(src, ~) 
% Prompt user for new label 
    newLabel = inputdlg('Enter new label:', 'Edit Label', 1, {src.String}); 
    if ~isempty(newLabel) 
        src.String = newLabel{1};  % Update the label 
    end 
end 

You might also find these references useful:

1. https://www.mathworks.com/help/matlab/ref/questdlg.html
2. https://www.mathworks.com/help/matlab/creating_plots/create-callbacks-for-graphics-objects.html

Hope this helps.