I'm trying to plot a spectrogram of a vibration signal using Matlab, but I'm not happy with the way that the spectrogram-function plots the signal (I would like to customize the axes and use a mapped vector instead of time). Right now I'm trying to plot the thing myself using pcolor:
[M_s, M_w, M_t] = spectrogram(M_i, 2^16, ceil(2^16*0.95), [0:0.2:15000], Sample_rate);
figure;
[M_t, M_w] = meshgrid(M_t, M_w);
h = pcolor(M_t, M_w, mag2db(abs(M_s)));
set(h, 'LineStyle', 'none);
However, doing this, my plotted figure is extremely slow and I can't really work with that, because it takes ages to zoom in or do anything with it. When I just use spectrogram to plot the figure, it's super fast. So my question is, what exactly does spectrogram do, to plot the figure?
Related
I am a bit struggling with my polar plot. I am playing with strikes and dips, and for each pair of those, an "intensity". I'd like to plot this surface/contourf/whatever function on my polarplot. I cannot find the handle to do so. Dpp2 contains the intensity value for a given theta and rho/ strike and dip.
xTmp = (0:4:360);
yTmp = (0:22.5:90);
[strike,dip]= meshgrid(deg2rad(xTmp),deg2rad(yTmp));
dip2 = rad2deg(dip);
strike2 =rad2deg(strike);
figure('name', 'COLD');
polarplot([0 360],[0 90]);
s = surf(strike2, dip2, DPp2);
polarplot(s);
colormap
I've tried something like that, which obviously doesn't work.
cheers,
Flo
As far as I know there is no way of creating a surface plot directly in a polarplot.
One workaround is to manually create your polar axis plot. You can find an example here.
Another workaround would be to use
polarscatter to create a scatter plot (which looks simmilar in case you have a tight grid) Have a look at this.
Because you mentioned the handle: In case you want a handle to the axes have a look at polaraxes from here.
The polar scatter wasn't working, so I tried another function, which seems to work according to this page: https://fr.mathworks.com/matlabcentral/answers/95796-how-do-i-create-a-contour-plot-in-polar-coordinates
I am note quite there yet, the contour map isn't "wrapped" around my polar plot, but so far it's compiling. If anyone has an idea on how to superimpose the contour map onto the polar plot ?
dip2 = rad2deg(dip);
strike2 =rad2deg(strike);
h = polar([0 360],[0 90]);
hold on;
contourf(strike2,dip2,DPp2);
% Hide the POLAR function data and leave annotations
set(h,'Visible','off')
% Turn off axes and set square aspect ratio
axis off
axis image
I am in need of plotting a 2D spectrogram of a signal in Matlab. I need it for a printed assignment, hence the 3D image makes no sense. However, when the signal is plotted using Spectrogram it automatically produces a 3D plot of the signal.
My Code:
Dataset = 1; % Dataset to be analysed
N = 1024; % Window size
Beta = 12; % Kaiser window beta value (small = narrow main lope)
Overlap = 800; % Window overlap
Threshold = -150; % Minimum magnitude before threshold
spectrogram(Enclosure{Dataset}(1:end),kaiser(N,Beta),Overlap,2048,fs,'MinThreshold',Threshold,'yaxis');
which produces a graph that looks like this:
But it is seen from the top, and the graph is really showing this:
The reason why i need it to specifically be 2D (and why i don't settle with a screenshot) is because i am using Matlab2tikz to convert Matlab figures into Tikz figures in LaTex. with the 3D images i get figures of +100 Mb and 2D will reduce the size to <1Mb.
I don't know what version of Matlab you are using but in 2015a you should be able to get a handle to the figure with the 3D plot and change the view angle to 2D:
view(0,90);
I've also got an example of how you can make your own 2D plot from the outputs of spectrogram() using a similar method:
x = [0:0.01:100];
y = sin(5*x);
y = awgn(y,0.1);
[S,F,T,P] = spectrogram(y,200,0,length(y)*5,100);
[m,n] = size(P);
figure(2)
surf(F,T,zeros(n,m),P','EdgeColor','none')
view(0,90)
xlabel('Frequency')
ylabel('Time (s)')
The output looks like this:
Hopefully since there is no altitude information, the figure size might be smaller but I can't test that since I don't have Matlab2tikz.
One option is to capture whatever its plotted and then plot it as an image. You can do this using getframe
if you do
F=getframe(gca);
cla;
imshow(F.cdata);
You'll get exactly what you will be seeing before, but as an image.
However I think it defeats a bit the purpose of Matlab2Tikz, as the idea os that you have Tikz code describing your data...
You can try the following:
[~,F,T,ps]=spectrogram(Enclosure{Dataset}(1:end),kaiser(N,Beta),Overlap,2048,fs,'MinThreshold',Threshold,'yaxis').
% Output the spectrum in ps
imagesc(T,F,10*log10(ps))
% Generate a 2d image
view(270,90)
xlabel('Time [s]')
ylabel('Frequency [Hz]')
c=colorbar;
c.Label.String='Power [dB]';
% Extra setting to make the plot look like the spectrogram
Good luck
I need assistance making a nice contour plot. I have data from an underwater glider that dives and climbs repeatedly from the surface of the ocean to around 30 m, in this case.
I think my issue is with interpolating the data, and I am not sure how to proceed. Here is the contour plot of density I have generated this far.
The Contour plot of density was generated using this code
xlin = linspace(min(time),max(time),500);
ylin = linspace(min(depth),max(depth),500);
[X,Y] = meshgrid(xlin,ylin);
Z = griddata(time,depth,density,X,Y);
[C,h] = contour(X,Y,Z,[1022.0, 1022.5, 1023.0, 1023.5, 1024.0, 1024.5, 1025.0, 1025.5, 1026.0],'color',[0.5 0.5 0.5]);
v = [1022.0, 1022.5, 1023.0, 1023.5, 1024.0, 1024.5, 1025.0, 1025.5, 1026.0];
clabel(C,h,v,'fontsize',8);
set(gca,'ydir','reverse');
I want the plot to have smooth contour lines. Once I get the contour plot to look good I will overlay it on salinity and temperature scatter plots.
Please let me know how I can make a better looking contour plot.
Is it an issue with interpolation? Or the way I gridded the data?
Thanks very much! Please be specific and give code examples if you've played with the data.
Here is the time, depth, and density matlab data: https://www.dropbox.com/s/agi70zh7haggf07/data.mat?dl=0
The problem is that bunch of your interpolated data are missing. I mean that Z has a bunch of NaNs:
xlin = linspace(min(time),max(time),500);
ylin = linspace(min(depth),max(depth),500);
[X,Y] = meshgrid(xlin,ylin);
Z = griddata(time,depth,density,X,Y);
%surf(X,Y,Z) %also interesting
spy(isnan(Z));
Result:
Your input data are somehow ill-defined, and griddata gives up. Here's why:
>> sum(isnan(density))
ans =
3174
Fix the NaNs in your raw data, and you'll most probably fix the plot.
Update
I threw away your NaNs:
inds=~isnan(density);
time=time(inds);
depth=depth(inds);
density=density(inds);
to see how the result looks like. It turns out that your original code is already looking OK to me!
Original on the left, de-NaNed version on the right:
So... maybe your datetime transformation is off? Or your time limits, not showed in your original code?
I am trying to create a smaller plot within a plot in MATLAB, for example like the image of this MATLAB File Exchange Upload.
There, two figures are created and then both of them are plotted in one figure.
My problem however is that I already have two MATLAB figures from earlier simulations and I need to embed one figure into the other one, i.e., one would be small and the other plot would be big but in the same graph. Could someone suggest an easy way to do this?
This can be done using the copyobj function. You'll need to copy the Axes object from one figure to the other:
f(1) = openfig('fig1.fig');
f(2) = openfig('fig2.fig');
ax(1) = get(f(1),'CurrentAxes'); % Save first axes handle
ax(2) = copyobj(get(f(2),'CurrentAxes'),f(1)); % Copy axes and save handle
Then you can move and resize both axes as you like, e.g.
set(ax(2),'Position', [0.6, 0.6, 0.2, 0.2]);
I have got a data of size 13558x100 and I am trying to plot it. For 2D, I could use:
plot(X(:,1), X(:,2))
How can I plot this big data? Can I just use surf to visualize the data or is there any other way?
As others have mentioned imagesc is the better way to go about this. It allows you to see a field of 2D data without a 3D plot using colour mapping. The toy example code is here.
Y = randn(13558,100);
figure; imagesc( Y );
This code generates the image as follows.
Furthermore, you can use the function colorbar to get a bar legend for your data.
colorbar;
After using the colorbar function, it generates the figure below.