I have a matrix of size 2000 by 300. When I try to plot a 3D graph using surf, it is very dark because of the amount of points. I tried different colors but it is still very dark. How do I plot the density of the graph instead of the 3D? Also, the original matrix was about 3000 times bigger than this (I had to decimate it to get to 2000x300). Do I need another kind of plot for the original one or does density plot work?
Thank you,
Try using mesh instead of surf, here is a sample code:
clear; close; clc;
A = rand(2000,300);
[xx,yy] = meshgrid(1:size(A,2),1:size(A,1));
mesh(xx,yy,A)
Related
I would like to be able to overlay isolines over a filled contour or surface as it is done in this figure:
Can matlab overlay contour and contourf plots?
So far, I have tried this:
[X,Y] = meshgrid(x_cases,y_cases);
Points = length(x_cases)*length(y_cases);
resX = reshape(X,Points,1);
resY = reshape(Y,Points,1);
resZ = reshape(DataGrid_a,Points,1);
scatter(resX,resY,[],resZ,’filled’)
hold on
contour(X,Y,DataGrid_b,'ShowText','on')
But I have to reduce the transparency of my scatter plot to be able to see the contour lines from DataGrid_b, it would be more ideal to not change the transparency and overlay my isolines. I appreciate any input you may give me!
Thanks!
The simplest solution (and it's very hack) is to take advantage of the fact that 2D plots are plotted at Z = 0; So put your scatter points at some Z value below that.
scatter3(resX,resY,-ones(size(resX)),[],resZ,’filled’)
view(2)
hold on
contour(X,Y,DataGrid_b,'ShowText','on')
I need to plot two plots on same figure in MATLAB.
The maximum and minimum values in both the data samples have large variation, which I am unable to plot by taking same y-axis limits.
I do not wish to use two scales as explained in other Overlaying two axes in a Matlab plot but need to use a single y-axis and get the solution.
I tried the code:
x_axis_X = 1:length(S);
y_axis_Y = 1:length(N);
ylim([-1204200 -1841.6])
set(gcf,'color','w');
plot(x_axis_X, S,'o-', y_axis_Y, N, 'x-');
The result is as shown in the plot where one data sample is plotted without proper y-axis range.
The y limits for first data sample is -1204200 to -1841.6 and for the second it is -489429345.5 to -10408189.43.
How should be the ylim defined to fit both plots in the same figure?
I appreciate your inputs. Thank you.
In older versions of MATLAB use the function plotyy. In more recent versions of MATLAB use yyaxis. The following is the example from the documentation:
x = linspace(0,10);
y = sin(3*x);
yyaxis left
plot(x,y)
z = sin(3*x).*exp(0.5*x);
yyaxis right
plot(x,z)
ylim([-150 150])
I tried the idea of scaling one dataset so that it has a similar magnitude as the other data set. Here, I multiplied one dataset by 100 (or any suitable scaling parameter), and then it will be similar in size to the other data set. In order to clearly mention which data has been scaled in the graph I used the legend.
plot(x,data1,x,100*data2)
legend('data1','100*data2','location','southeast')
Thank you.
Scaling is not the best option, as you may need to work with the data later. Also does not work if for instance, you need a log scale.
Matlab has a few ways to deal it with. I particularly like to use a new axes in the figure, as i have done in the example below.
Just in case, you also found this answer in a simple google search!
Code:
a=1:10;
b=(10:-1:1)*100;
x=1:10;
hold on
plot(x,a,'b')
pax1=get(gca,'Position'); %get axis position
ax2 = axes('Position',pax1); %create a new axis
plot(ax2,x,b,'r') %plot new data
set(ax2, 'Yaxislocation','right',...
'color','none') % set it transparent and to the right
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 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.
I want to know how to plot the contour of the FFT of an image in Matlab. I have this code but when plotting the contour I get a blue plot. I think I need to specify the range of the frequencies in the contour function, but how to know/compute the range?
monolayer = double(imread('TEM_monolayer_graphene.bmp'));
monolayerFFTs = fftshift(fft2(monolayer));
contour(monolayerFFTs);
I think instead of the blue plot I should get a 3D plot with some spikes at the frequencies where there is more energy.
I was able to get a really good plot with the following code
monolayer = double(imread('TEM_monolayer_graphene.bmp'));
monolayerFFTs = fftshift(fft2(monolayer));
contour(abs(monolayerFFTs));