Can't produce multiple Circles

Hi!

I am currently trying to create multiple circles on App Designer. The idea of this project is that the user is meant to insert the x,y and radius inputs and it should be plotted on the graph/axes.

I have tried to write some code, but it just wouldn't plot for some reason. This is from the last question I asked, but I am posting again due to urgency and need to finish this project ASAP.

Would appreciate all the assistance I can get!! Thank you!!

% 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-')

Answer 1

[Image Analyst]

It's simple to adapt. Not sure you tried to adapt it since it's the same snippet I gave you before. Anyway, try this:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
% Ask user for two floating point numbers.
defaultValue = {'5', '2', '3'};
titleBar = 'Enter values';
userPrompt = {'Enter x : ', 'Enter y: ', 'Enter Radius'};
caUserInput = inputdlg(userPrompt, titleBar, 1, defaultValue);
if isempty(caUserInput),return,end % Bail out if they clicked Cancel.
% Convert to floating point from string.
x = str2double(caUserInput{1})
y = str2double(caUserInput{2})
radius = str2double(caUserInput{3})
% Check usersValue1 for validity.
if isnan(x)
    % 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.
    x = str2double(defaultValue{1});
    message = sprintf('I said it had to be a number.\nTry replacing the user.\nI will use %.2f and continue.', x);
    uiwait(warndlg(message));
end
% Do the same for usersValue2
% Check usersValue2 for validity.
if isnan(y)
    % 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.
    y = str2double(defaultValue{2});
    message = sprintf('I said it had to be a number.\nTry replacing the user.\nI will use %.2f and continue.', y);
    uiwait(warndlg(message));
end
% Do the same for usersValue3
% Check usersValue3 for validity.
if isnan(radius)
    % 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.
    radius = str2double(defaultValue{3});
    message = sprintf('I said it had to be a number.\nTry replacing the user.\nI will use %.2f and continue.', y);
    uiwait(warndlg(message));
end
angles  = linspace(0, 2 * pi, 400);
xCircle = x + radius*cos(angles);
yCircle = y + radius*sin(angles);
plot(xCircle, yCircle, 'r-', 'LineWidth', 2)
grid on;
axis equal

Anyway, if you're using app designer you wouldn't use inputdlg() - you'd place edit text boxes on the window and get the numbers from there, like

x = str2double(app.edtX.Text);
y = str2double(app.edtY.Text);
radius = str2double(app.edtRadius.Text);

[Dev Chhatbar]

@Image Analyst Whoa. You're a genius!!! This is phenomenal! I am sorry, I am new to Matlab and this is a huge learning process for me ahah! That code works brilliantly. We're allowed to use inputdlg() as per the requirements. Out of curiosity, since this builds one circle, is it possible to build another one on the same graph? Or maybe have it such that it is portrayed on the app.UIAxes, where I could go on to add other points and draw lines on it perhaps? I would appreciate all the help!!!

[Dev Chhatbar]

I tried doing this but it shows an error

plot(app.UIAxes, xCircle, yCircle, 'r-', 'LineWidth', 2)

Unable to resolve the name 'app.UIAxes'.

The error is: "Reference to a cleared variable app."

I am guessing it wants me to refer to the thing correctly, but that's what it's called when I read in the Component browser.

[Dev Chhatbar]

@Image Analyst Hope this gives you an idea of what I am after. Would appreciate your assistance.

[Image Analyst]

You need to put it into a loop.

buttonText = 'Continue';
while contains(buttonText, 'Continue')
    % Draw circle using existing code.
    hold on; % Con't let subsequent circles blow away prior circles.
    % Ask user if they want to draw another circle
    promptMessage = sprintf('Do you want to Continue drawing circles,\nor Quit processing?');
    titleBarCaption = 'Continue?';
    buttonText = questdlg(promptMessage, titleBarCaption, 'Continue', 'Quit', 'Continue');
    if contains(buttonText, 'Quit', 'IgnoreCase', true)
    	return; % or break or continue.
    end
end

Still, the best way is to just have a GUI up with 3 edit fields and a "Draw circle" button.

Look in the design view. You should have an axes control with the name UIAxes. If you do, then somewhere in your code you deleted it, like maybe you called clear or delete.

[Dev Chhatbar]

I will attach an image of what my GUI looks like so far. Whatever you have mentioned so far is what's on there. I have been trying to connect the UIAxes to the code, but for whatever reason it just wouldn't plot it on there?? Really don't know what's going on?!

[Image Analyst]

Attach your .mlapp file with the paperclip icon.

[Dev Chhatbar]

Sure!

[Dev Chhatbar]

@Image Analyst Here's my app, just as you asked. Any ideas on what's missing? I am also running out of time as this is due tomorrow. So would appreciate all sorts of help!

[Voss]

"The error is: "Reference to a cleared variable app.""

@Dev Chhatbar: Don't use clear within an app.

[Dev Chhatbar]

@Voss-- That works!!! WHAT!! Damn! How would I now go on to draw an extra circle on the same Axes? And furthermore go on to draw tangential lines?? Would appreciate your assistance!!

[Image Analyst]

Thanks to @Voss for reminding you. I had already told you "If you do, then somewhere in your code you deleted it, like maybe you called clear or delete." but I guess you overlooked that.

You can use hold on to draw multiple circles, or simply use viscircles.

To find the tangent line you need to specify the x and y point where the tangent line touches the circle. Then you need to get the slope of the line via the derivative dy/dx of the equation (x-xc)^2 + (y-yc)^2 = radius^2. Solve for y then take the derivative. I trust you can do that if you've taken calculus.

[Dev Chhatbar]

I see, My bad @Image Analyst. You were right. The code that you added up there which allows me to ask the user to continue drawing circles, works somewhat? In the sense that, it pops up with the prompt but doesn't go further to allow the user to input the info. Also, kinda embarrassing, but my Calculus isn't the best. I am currently studying it and trying to master but it's still very poor. :( This is pretty bad. I am now in panic mode ahah as this thing is due at 9 in the morning tomorrow :(

[Image Analyst]

After you call inputdlg() you call plot(). I showed you that in my original answer so I don't know what you mean when you say it doesn't do anything beyond the inputdlg() prompt window.

Sorry you'll miss your deadline. I'm about to head to bed for the night.

[Dev Chhatbar]

Hah! Not to worry! I have finished the project and submitted it! Thank you for everything!! Have a good night!

[Image Analyst]

If this Answer solves your original question, then could you please click the "Accept this answer" link to award the answerer with "reputation points" for their efforts in helping you? They'd appreciate it. Thanks in advance. 🙂 Note: you can only accept one answer (so pick the best one) but you can click the "Vote" icon for as many Answers as you want. Voting for an answer will also award reputation points.