How can I make it so that the value from my slider changes the rotation speed of the ferris wheel in my code?

Hi, I am trying to write code so that I can slide the slider and the value it corresponds to is the value p in my code which changes the rotation speed of the ferris wheel. I'm not sure where I went wrong in the code. Thanks!

slider = uicontrol('Style','slider','Min',0,'Max',100,'Value',0, 'SliderStep',[0.1 0.1], ...
    'Units', 'normalized', 'Position', [0.1 0.01 0.8 0.03], Callback, {@sliderCallback});
p=sliderCallback(slider,'Value');

where p plays a part here in the movement of my ferris wheel: the smaller p is, the smaller amount of time each frame will pause for therefore it will seem like the baskets on my ferris wheel are rotating faster.

moving_basket2=translateShape(basket2,-10*cos(n+(pi/2)),-10*sin(n+(pi/2))-10); % Creates fourth basket
drawshape(moving_basket2,"m");
fill(moving_basket2(1,:),moving_basket2(2,:),"m")
axis([-18 28 -18 18]) % Sets axis by defining xmin, xmax, ymin, ymax
pause(p) % Animates the baskets
hold off % Ensures that only one frame of each basket is displayed at a time
end

my sliderCallback function is:

function a=sliderCallback(slider,event)
val=get(slider,'Value');
a=val
end

Answer 1

[VBBV]

Delete the return value for sliderCallback function call as shown below and put the while and/or for loop code for the animation of baskets inside the sliderCallback function

s = uicontrol('Style','slider','Min',0,'Max',100,'Value',0, 'SliderStep',[0.1 0.1], ...
    'Units', 'normalized', 'Position', [0.1 0.01 0.8 0.03]);
s.Callback = @sliderCallback   % call the function for slider value
function sliderCallback(slider,event)  % delete the return value for sliderCallback function 
    val=get(slider,'Value');
    p=val
    % use the value of p in the loop to animate the baskets 
    %while 1  % put the loop part in your code inside the slidercallback
    %function 
    moving_basket2=translateShape(basket2,-10*cos(n+(pi/2)),-10*sin(n+(pi/2))-10); % Creates fourth basket
    drawshape(moving_basket2,"m");
    fill(moving_basket2(1,:),moving_basket2(2,:),"m")
    axis([-18 28 -18 18]) % Sets axis by defining xmin, xmax, ymin, ymax
    pause(p) % Animates the baskets
    hold off % Ensures that only one frame of each basket is displayed at a time
    %end
    
end

[Vicky]

Do I need to actually use the function sliderCallback somewhere in my main script? If so, what actually is 'event'?

Or is line in the main script the only place sliderCallback needs to appear?

s.Callback = @sliderCallback % call the function for slider value

in the main script the only place sliderCallback needs to appear?

[VBBV]

If so, what actually is 'event'?

event detects the action done with App or GUI component by user.

Do I need to actually use the function sliderCallback somewhere in my main script?

Or is line in the main script the only place sliderCallback needs to appear?

sliderCallback function can be invoked from the mainscript file. You can either put the function in the main script file or outside the main script file. If you place function code outside the mainscript, then all the related functions need to be put in the same folder, otherwise you would get path errors.

Answer 2

[Walter Roberson]

slider = uicontrol('Style','slider','Min',0,'Max',100,'Value',0, 'SliderStep',[0.1 0.1], ...
    'Units', 'normalized', 'Position', [0.1 0.01 0.8 0.03], Callback, {@sliderCallback});

The initialization of slider sets sliderCallback as the callback function. When that function is invoked because of a callback, any value it returns will be ignored.

p=sliderCallback(slider,'Value');

That will call the function once and will probably return a value of 0 because that is what the properties are initialized to.

pause(p) % Animates the baskets

You need to have that p updated every iteration of the loop, so before that line you should add in

p = slider.Value;

[Vicky]

Thanks! But it still doesn't work for some reason, I get an error in the line slider=uicontrol.....

Is there something wrong with the code of my sliderCallback function?