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# How can I use obw function in App Designer?

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Albert Chan on 24 Sep 2019
Answered: Bhargavi Maganuru on 11 Oct 2019
According to obw function described in https://www.mathworks.com/help/signal/ref/obw.html,
how can I apply it with UI.Axes in App Designer?
Thanks in advance!

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### Answers (1)

Bhargavi Maganuru on 11 Oct 2019
obw” function without output arguments returns PSD plot in the current figure window and annotates the bandwidth. As gcf cannot return an App Designer figure and gca cannot return any axes within App Designer figure, so obw plot gets plotted in figure window outside App Designer and not in the UIAxes.
Instead you can plot PSD plot(using FFT) and annotate the bandwidth(using “obw”) in the UIAxes.
N = length(x);
xdft = fft(x);
xdft = xdft(1:N/2+1);
psdx = (1/(Fs*N)) * abs(xdft).^2;
psdx(2:end-1) = 2*psdx(2:end-1);
freq = 0:Fs/length(x):Fs/2;
plot(app.UIAxes, freq,10*log10(psdx));
And then annotate the bandwidth using output arguments of “obw” function and xline function
[bw,flo,fhi,power]=obw(x,Fs) % returns the lower and upper bounds of the occupied bandwidth and the occupied band power.
For more information about “obw” function refer to the link :https://in.mathworks.com/help/signal/ref/obw.html
Hope this helps!

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