Azzera filtri
Azzera filtri

Plotting matrix as spectrogram

16 visualizzazioni (ultimi 30 giorni)
Sania Gul
Sania Gul il 26 Ago 2022
Commentato: Robert U il 26 Ago 2022
I want to plot a matrix of 256* 16, as spectrogram. But when I use surf command to do so, I got spectrogram of size 343*436. I want the image to be of same size as that of matrix i.e. 256*16. Kindly suggest any solution without cropping or resizing the image as both of them distorts the quality.
  3 Commenti
Robert U
Robert U il 26 Ago 2022
testData = randn(256,16);
fh = figure;
ah = axes(fh);
surf(ah,testData);
I was not able to reproduce the described error by the given information.
Kind regards,
Robert
Sania Gul
Sania Gul il 26 Ago 2022
[Q,F,T] = spectrogram(audio,hann(512),256,512,Fs,'yaxis');
Q=Q(1:256,:);
F=F(1:256);
figure(2)
D=surf(T,F,log(abs(Q).^2));
colormap parula
shading interp
view([0 90])
axis tight
set(gca,'xtick',[])
set(gca,'ytick',[])
export_fig AA.jpg -native -c[31 52 46 72]% top right bottom left
% reading the image
I=imread('AA.jpg');
>>The value of I=343x436x3 uint8, but the size of matrix Q was only 256x16, and I want 'I' to be also 256x16x3 uint8

Accedi per commentare.

Risposta accettata

Robert U
Robert U il 26 Ago 2022
Hi Sania Gul,
The values you provide are not consistent. I assume your "audio" is a vector of a certain length N, sampled with the frequency Fs.
Applying the function spectrogram with the window-length 512, overlap 256 and NFFT of 512 lead certainly to the dimension of Q of NFFT/2+1 = 257 and ((N - 512)/(512-256)).
If you want Q to be 257 x 16 you would have to provide a snippet of roughly 4600 samples.
fs = 60e3;
t = 0:1/fs:4599/fs;
x1 = vco(sawtooth(2*pi*t,0.5),[0.1 0.4]*fs,fs);
[Q,F,T] = spectrogram(x1,hann(512),256,512,fs,'yaxis');
size(Q)
ans = 1×2
257 16
Kind regards,
Robert
  4 Commenti
Sania Gul
Sania Gul il 26 Ago 2022
Tnk u soooo much, but how to get rid of the frame around the spectrogram without using the export.fig?
Robert U
Robert U il 26 Ago 2022
There is still some manual work required to get the desired result.

Accedi per commentare.

Più risposte (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by