Errors in converting real time sine wave in it's real time Fourier transform. The graph in UI Axes for frequency domain is not getting plotted in real time

Question

Anupriya Bhardwaj 2021-12-7

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1604915-errors-in-converting-real-time-sine-wave-in-it-s-real-time-fourier-transform-the-graph-in-ui-axes-f

回答： prabhat kumar sharma 2024-5-2

I have created an app in which two axes are used one for plotting sine wave in time domain and other in frequency. The wave is being ploteed in time domain but not in frequency domain. Please help me

the code is as follows:

classdef app_4 < matlab.apps.AppBase

% Properties that correspond to app components

properties (Access = public)

UIFigure matlab.ui.Figure

NoiseAmplitudeSlider matlab.ui.control.Slider

NoiseAmplitudeSliderLabel matlab.ui.control.Label

SinefrequencySlider matlab.ui.control.Slider

SinefrequencySliderLabel matlab.ui.control.Label

SineAmplitudeSlider matlab.ui.control.Slider

SineAmplitudeSliderLabel matlab.ui.control.Label

UIAxes2 matlab.ui.control.UIAxes

UIAxes matlab.ui.control.UIAxes

end

% Callbacks that handle component events

methods (Access = private)

% Value changed function: SineAmplitudeSlider

function SineAmplitudeSliderValueChanged(app, event)

value = app.SineAmplitudeSlider.Value;

f=app.SinefrequencySlider.Value;

a=app.SineAmplitudeSlider.Value;

w=2*pi*f;

na=app.NoiseAmplitudeSlider.Value;

t=0:0.01:100*pi;

x=a*sin(w*t);

nfft=100;

n=numel(t);

y=na*rand(1,length(t));

sine=x+y;

for i=1:n

plot(app.UIAxes,t(1:i),sine(1:i));

drawnow;

end

nfft=1024;

sine=sfft(x,nfft);

sine=sine(1:nfft/2);

mx=abs(sine);

fs=(0:nfft/2-1)*f/nfft;

m=numel(m);

for j=1:m

plot(app.UIAxes2,fs(1:j),mx(1:j));

drawnow;

end

% Value changed function: SinefrequencySlider

function SinefrequencySliderValueChanged(app, event)

value = app.SinefrequencySlider.Value;

f=app.SinefrequencySlider.Value;

a=app.SineAmplitudeSlider.Value;

w=2*pi*f;

na=app.NoiseAmplitudeSlider.Value;

t=0:0.01:100*pi;

x=a*sin(w*t);

nfft=100;

n=numel(t);

y=na*rand(1,length(t));

sine=x+y;

for i=1:n

plot(app.UIAxes,t(1:i),sine(1:i));

drawnow;

end

nfft=1024;

sine=sfft(x,nfft);

sine=sine(1:nfft/2);

mx=abs(sine);

fs=(0:nfft/2-1)*f/nfft;

m=numel(m);

for j=1:m

plot(app.UIAxes2,fs(1:j),mx(1:j));

drawnow;

end

% Value changed function: NoiseAmplitudeSlider

function NoiseAmplitudeSliderValueChanged(app, event)

value = app.NoiseAmplitudeSlider.Value;

f=app.SinefrequencySlider.Value;

a=app.SineAmplitudeSlider.Value;

w=2*pi*f;

na=app.NoiseAmplitudeSlider.Value;

t=0:0.01:100*pi;

x=a*sin(w*t);

nfft=100;

n=numel(t);

y=na*rand(1,length(t));

sine=x+y;

for i=1:n

plot(app.UIAxes,t(1:i),sine(1:i));

drawnow;

end

nfft=1024;

sine=sfft(x,nfft);

sine=sine(1:nfft/2);

mx=abs(sine);

fs=(0:nfft/2-1)*f/nfft;

m=numel(m);

for j=1:m

plot(app.UIAxes2,fs(1:j),mx(1:j));

drawnow;

end

% Component initialization

methods (Access = private)

% Create UIFigure and components

function createComponents(app)

% Create UIFigure and hide until all components are created

app.UIFigure = uifigure('Visible', 'off');

app.UIFigure.Position = [100 100 790 489];

app.UIFigure.Name = 'MATLAB App';

% Create UIAxes

app.UIAxes = uiaxes(app.UIFigure);

title(app.UIAxes, 'TIME DOMAIN')

xlabel(app.UIAxes, 'X')

ylabel(app.UIAxes, 'Y')

zlabel(app.UIAxes, 'Z')

app.UIAxes.XLim = [0 10];

app.UIAxes.YLim = [-10 10];

app.UIAxes.XAxisLocation = 'origin';

app.UIAxes.YAxisLocation = 'origin';

app.UIAxes.Position = [297 260 475 208];

% Create UIAxes2

app.UIAxes2 = uiaxes(app.UIFigure);

title(app.UIAxes2, 'Frequency Domain')

xlabel(app.UIAxes2, 'X')

ylabel(app.UIAxes2, 'Y')

zlabel(app.UIAxes2, 'Z')

app.UIAxes2.YLim = [-10 10];

app.UIAxes2.XAxisLocation = 'origin';

app.UIAxes2.YAxisLocation = 'origin';

app.UIAxes2.Position = [297 25 475 212];

% Create SineAmplitudeSliderLabel

app.SineAmplitudeSliderLabel = uilabel(app.UIFigure);

app.SineAmplitudeSliderLabel.HorizontalAlignment = 'right';

app.SineAmplitudeSliderLabel.Position = [1 429 86 22];

app.SineAmplitudeSliderLabel.Text = 'Sine Amplitude';

% Create SineAmplitudeSlider

app.SineAmplitudeSlider = uislider(app.UIFigure);

app.SineAmplitudeSlider.Limits = [0 10];

app.SineAmplitudeSlider.ValueChangedFcn = createCallbackFcn(app, @SineAmplitudeSliderValueChanged, true);

app.SineAmplitudeSlider.Position = [108 438 150 3];

% Create SinefrequencySliderLabel

app.SinefrequencySliderLabel = uilabel(app.UIFigure);

app.SinefrequencySliderLabel.HorizontalAlignment = 'right';

app.SinefrequencySliderLabel.Position = [1 352 86 22];

app.SinefrequencySliderLabel.Text = 'Sine frequency';

% Create SinefrequencySlider

app.SinefrequencySlider = uislider(app.UIFigure);

app.SinefrequencySlider.Limits = [0 10];

app.SinefrequencySlider.ValueChangedFcn = createCallbackFcn(app, @SinefrequencySliderValueChanged, true);

app.SinefrequencySlider.Position = [108 361 150 3];

% Create NoiseAmplitudeSliderLabel

app.NoiseAmplitudeSliderLabel = uilabel(app.UIFigure);

app.NoiseAmplitudeSliderLabel.HorizontalAlignment = 'right';

app.NoiseAmplitudeSliderLabel.Position = [1 289 126 22];

app.NoiseAmplitudeSliderLabel.Text = 'Noise Amplitude Slider';

% Create NoiseAmplitudeSlider

app.NoiseAmplitudeSlider = uislider(app.UIFigure);

app.NoiseAmplitudeSlider.Limits = [0 10];

app.NoiseAmplitudeSlider.ValueChangedFcn = createCallbackFcn(app, @NoiseAmplitudeSliderValueChanged, true);

app.NoiseAmplitudeSlider.Position = [148 298 150 3];

% Show the figure after all components are created

app.UIFigure.Visible = 'on';

end

% App creation and deletion

methods (Access = public)

% Construct app

function app = app_4

% Create UIFigure and components

createComponents(app)

% Register the app with App Designer

registerApp(app, app.UIFigure)

if nargout == 0

clear app

end

% Code that executes before app deletion

function delete(app)

% Delete UIFigure when app is deleted

delete(app.UIFigure)

end

I have bold the code made by me. Please do let me know what is the error.

2 个评论
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KSSV 2021-12-7

You must specify the error you are getting.

Anupriya Bhardwaj 2021-12-7

I have mentioned that I have two UI Axes and in first one time domain is being plotted but in second one after using fft function the graph is not being plotted. So, it will be a great help because I am not able to find my mistake.

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Answer 1

prabhat kumar sharma 2024-5-2

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1604915-errors-in-converting-real-time-sine-wave-in-it-s-real-time-fourier-transform-the-graph-in-ui-axes-f#answer_1451091

在 MATLAB Online 中打开

Hi Anupriya,

I understand you are facing issue in frequency domain plotting section. Specifically, there are a couple of mistakes that need to be corrected for the frequency domain plot to work correctly. Here's a breakdown of the issues and how to fix them:

Incorrect Function for FFT: You've used sfft(x,nfft) which seems to be a typo or an undefined function. The correct MATLAB function for computing the Fast Fourier Transform (FFT) is fft.'

For More information on fourier tranform please refer the below documentation:

FFT : https://www.mathworks.com/help/matlab/ref/fft.html

STFT : https://www.mathworks.com/help/signal/ref/stft.html

Incorrect Handling of m Variable: You have a line m=numel(m); which doesn't make sense because m is not defined before this line. You likely intended to find the number of elements in another variable, possibly mx or fs.
Plotting the Frequency Domain Data: The loop for plotting the frequency domain data seems unnecessary and might cause the plot to update very slowly, especially with drawnow inside the loop. Instead, you can plot the entire dataset at once.

Here's the refrence code for the corrected section of your code for the SineAmplitudeSliderValueChanged function, which should also be applied to the other slider value changed functions (SinefrequencySliderValueChanged, NoiseAmplitudeSliderValueChanged):

% Value changed function: SineAmplitudeSlider
function SineAmplitudeSliderValueChanged(app, event)
    f = app.SinefrequencySlider.Value;
    a = app.SineAmplitudeSlider.Value;
    w = 2 * pi * f;
    na = app.NoiseAmplitudeSlider.Value;
    t = 0:0.01:100 * pi;
    x = a * sin(w * t);
    nfft = 1024; % FFT points
    y = na * rand(1, length(t));
    sine = x + y;
    plot(app.UIAxes, t, sine); % Plot in time domain
    % Correct FFT usage
    Y = fft(sine, nfft);
    Y = Y(1:nfft/2); % Take the first half of FFT result
    mx = abs(Y);
    fs = (0:nfft/2 - 1) * (1 / (2 * pi)) * f / (nfft / 2); % Correct frequency scale
    plot(app.UIAxes2, fs, mx); % Plot in frequency domain
end