How to extract a part of the spectrogram?

Hi, I need help. How can I crop a part of the spectrogram? For example in the figure below I need to cut out the part of the spectrogram marked in red with the letter "A" and save it as an image.

Thank you for your help.

Answer 1

[Adam Danz]

Three approaches to selecting a range within a spectogram

Use saveas to save figures as any format.

1. Simple xlim & ylim

A simple approach that will not result in the loss of data would be to set xlim and ylim.

Demo:

% Full spectrogram
N = 512;
n = 0:N-1;
x = exp(1j*pi*sin(8*n/N)*32);
figure()
spectrogram(x,32,16,64,'centered','yaxis')
title('Full Spectrogram')
rectX = [120 270];  % x limits of selected range
rectY = [-.8 .8];   % y limits of selected range
ax = gca(); 
axis(ax, 'tight')
rectangle(ax, 'Position', [rectX(1), rectY(1), range(rectX), range(rectY)])

% Limit the visible range
figure()
spectrogram(x,32,16,64,'centered','yaxis')
ax = gca();
rectX = [120 270];  % x limits of selected range
rectY = [-.8 .8];   % y limits of selected range
xlim(ax, rectX)
ylim(ax, rectY)
title('Limited range using xlim & ylim')

2. Maintain DataAspectRatio

figure()
spectrogram(x,32,16,64,'centered','yaxis')
ax = gca();
originalDAR = ax.DataAspectRatio; 
rectX = [120 270];  % x limits of selected range
rectY = [-.8 .8];   % y limits of selected range
xlim(ax, rectX)
ylim(ax, rectY)
ax.DataAspectRatio = originalDAR;
title('Maintain data asepct ratio')

3. Maintain the region's area within the figure

figure()
spectrogram(x,32,16,64,'centered','yaxis')
ax = gca();
axis(ax, 'tight')

rectX = [120 270];  % x limits of selected range
rectY = [-.8 .8];   % y limits of selected range

% Scale axis position 
axPos = ax.Position; 
xl = xlim(ax); 
yl = ylim(ax); 
xScale = range(rectX)/range(xl); 
yScale = range(rectY)/range(yl); 
xShift = (rectX(1)-xl(1))/range(xl); 
yShift = (rectY(1)-yl(1))/range(yl); 

xlim(ax, rectX)
ylim(ax, rectY)

ax.Position(3) = axPos(3)*xScale; 
ax.Position(4) = axPos(4)*yScale;

ax.Position(1) = axPos(1) + xShift;
ax.Position(2) = axPos(2) + yShift;

title('Maintain region''s area within the figure')

[Antonio Spera]

hello thank you for the answer, I tried your solution and I wanted to ask you and I am attaching the result.

Is it possible to represent this, however, using the original time as the x axis? I would need an image like this:

[Adam Danz]

I've appended my answer with two alternatives. The second one is probably what you're looking for.

[Antonio Spera]

the second solution helped me to solve the problem, thank you very much.

[Adam Danz]

Socially-distant high-five! 🖐

[Antonio Spera]

🖐