How do I draw circles in App Designer with user inputting the x, y and radii values?

Hi,

So i am creating a project where I need to be able to draw multiple circles with different x, y and radii values. I was able to make one circle but it had a fixed radius and I would like it to be such that the user can input the different values and that is then used to plot the circle. This is what I have written down so far. I would appreciate any help I can get!

            clear;
            r    = 4;
            caca = 2*pi;
            ang  = linspace(0,caca);
            xp   = r*cos(ang);
            yp   = r*sin(ang);
            circ = [xp;yp];
            figure(1)
            plot(xp,yp)

I tried writing:

            r = inputdlg;

but it just wouldn't work. I mean it would allow the user to input the value but wouldn't plot a circle.

Any ideas on how I can get the user to enter the x, y and radii values and have it plot perfectly on a graph. I also want it to plot multiple circles.

Thank you!

Answer 1

[VBBV]

In the app designer, you can invoke the follwing code,

% in the app designer 
prompt = {'Enter radius of circle:', 'Enter centre:'}
T_L = 'Circle'
dims = [1 40]
out = inputdlg(prompt,T_L,dims)
caca = 2*pi;
ang  = linspace(0,caca);
r = str2num(out{1});
C = str2num(out{2});
xp = C(1)*cos(ang);
yp = C(2)*sin(ang);             
plot(xp,yp,'r-')

[Dev Chhatbar]

That works! Thank you! Would it possible by anyway to format it such that I could draw multiple circles on the same Axes? Because I want to be able to find the intersection between these circles? Hope I make sense.

[Image Analyst]

Yes, use viscircles to draw a bunch in one function call. Requires the Image Processing Toolbox I believe.

[Image Analyst]

If you want the user to indicate where they are you can use drawpoint or drawcircle

[Dev Chhatbar]

@Image Analyst I don't think I can afford to purchase that toolbox lol. How else can I get it to show on the axes? Also for some reason the above code works, but it goes down to the negative values on the axes, I want to find the intersections between these circles and be able to draw lines on them. Would appreciate your assistance!!

[Dev Chhatbar]

@Image Analyst, @VBBV -- the drawpoint and drawcircle do work. I just want it to be able to create the shape with the input from the user. Such that upon entering the value of the radius or the x and y coordinates, its put up on the axes. And then I can go on to write functions to draw tangent lines between the circles etc.

[Image Analyst]

If you don't want the user to click to define a center point with drawpoint you can use getinput(). If you won't want the user to click and drag out a circle interactively, you can ask them on your GUI, or you can call inputdlg Adapt this snippet as needed, but I think it's not convenient for your user as compared to clicking on the image.

% Ask user for two floating point numbers.
defaultValue = {'45.67', '78.91'};
titleBar = 'Enter values';
userPrompt = {'Enter floating point number 1 : ', 'Enter floating point number 2: '};
caUserInput = inputdlg(userPrompt, titleBar, 1, defaultValue);
if isempty(caUserInput),return,end % Bail out if they clicked Cancel.
% Convert to floating point from string.
usersValue1 = str2double(caUserInput{1})
usersValue2 = str2double(caUserInput{2})
% Check usersValue1 for validity.
if isnan(usersValue1)
    % They didn't enter a number.
    % They clicked Cancel, or entered a character, symbols, or something else not allowed.
    % Convert the default from a string and stick that into usersValue1.
    usersValue1 = str2double(defaultValue{1});
    message = sprintf('I said it had to be a number.\nTry replacing the user.\nI will use %.2f and continue.', usersValue1);
    uiwait(warndlg(message));
end
% Do the same for usersValue2
% Check usersValue2 for validity.
if isnan(usersValue2)
    % They didn't enter a number.
    % They clicked Cancel, or entered a character, symbols, or something else not allowed.
    % Convert the default from a string and stick that into usersValue2.
    usersValue2 = str2double(defaultValue{2});
    message = sprintf('I said it had to be a number.\nTry replacing the user.\nI will use %.2f and continue.', usersValue2);
    uiwait(warndlg(message));
end

[Dev Chhatbar]

@Image Analyst Thank you! I see what you mean (slightly). To plot on the axes would I write:

plot(usersvalue1,usersvalue2)??

I also don't think that would produce a circle? LIke how do i program that into the code?

[Dev Chhatbar]

@VBBV, @Image Analyst This is what my code looks like right now. Have to say, it's not functioning.

% Ask user for two floating point numbers.
                defaultValue = {'45.67', '78.91'};
                titleBar = 'Enter values';
                userPrompt = {'Enter floating point number 1 : ', 'Enter floating point number 2: '};
                caUserInput = inputdlg(userPrompt, titleBar, 1, defaultValue);
                if isempty(caUserInput),return,end % Bail out if they clicked Cancel.
                % Convert to floating point from string.
                usersValue1 = str2double(caUserInput{1})
                usersValue2 = str2double(caUserInput{2})
                % Check usersValue1 for validity.
                if isnan(usersValue1)
                    % They didn't enter a number.
                    % They clicked Cancel, or entered a character, symbols, or something else not allowed.
                    % Convert the default from a string and stick that into usersValue1.
                    usersValue1 = str2double(defaultValue{1});
                    message = sprintf('I said it had to be a number.\nTry replacing the user.\nI will use %.2f and continue.', usersValue1);
                    uiwait(warndlg(message));
                end
                % Do the same for usersValue2
                % Check usersValue2 for validity.
                if isnan(usersValue2)
                    % They didn't enter a number.
                    % They clicked Cancel, or entered a character, symbols, or something else not allowed.
                    % Convert the default from a string and stick that into usersValue2.
                    usersValue2 = str2double(defaultValue{2});
                    message = sprintf('I said it had to be a number.\nTry replacing the user.\nI will use %.2f and continue.', usersValue2);
                    uiwait(warndlg(message));
                end
                T_L = 'Circle'
                dims = [1 40]
                caca = 2*pi;
                ang  = linspace(0,caca);
                r = str2double(caUserInput{1});
                C = str2double(caUserInput{2});
                xp = C(1)*cos(ang);
                yp = C(2)*sin(ang);             
                plot(xp,yp,'r-')
                

[Image Analyst]

So you have two inputs? What do they mean? I thought you needed x, y, and radius? So that would be three things your user would have to enter.

[Dev Chhatbar]

@Image Analyst- Yes! That's a good point. I wonder why I didn't change that. You're right. Those are three things my user would need to enter. And based off of that, I'm meant to apply those inputs and plot the circles and then find the intersection point and draw tangential lines!

[Image Analyst]

I believe I fixed it for you in your duplicate question.