how to do density plot?
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sourabh mittal
el 19 de Sept. de 2018
Comentada: sourabh mittal
el 20 de Sept. de 2018
suppose, I have a text file 'data.txt' that has three columns and contains output of below.
% code
fileID = fopen('data.txt','w');
for x = 0.1:0.1:10
for y = 0.1:0.1:10
z = x*y;
T = [x, y, z];
fprintf(fileID,'%f %f %f\n',T);
end
end
fclose(fileID);
Now i want to do the density plot of this data. Please help.
4 comentarios
Adam Danz
el 19 de Sept. de 2018
I continued in the answer section though I'm unsure about the plot you're describing.
Respuesta aceptada
Image Analyst
el 19 de Sept. de 2018
Try this vectorized approach with meshgrid():
% Generate the data.
xv = 0.1:0.1:10
yv = 0.1:0.1:10
[x, y] = meshgrid(xv, yv)
z = x .* y
T = [x(:), y(:), z(:)]
% Show the x,y,z data as a surface
surf(xv, yv, z, 'EdgeColor', 'none');
xlabel('x', 'FontSize', 20);
ylabel('y', 'FontSize', 20);
zlabel('z', 'FontSize', 20);
% Write the file.
filename = fullfile(pwd, 'data.txt');
fileID = fopen(filename, 'wt');
fprintf(fileID,'%f %f %f\n',T'); % Don't forget to transpose with '
fclose(fileID);
type(filename);
% delete(filename);
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/196049/image.png)
3 comentarios
Image Analyst
el 19 de Sept. de 2018
OK. I thought you were going to visualize the data in the same program that created it. But it looks like Adam alerted you to the function dlmread(). But you might still look at my vectorized way of using meshgrid() - it's a handy function that allows you to do in one line what would otherwise be a multi line set of nested for loops.
Anyway, after calling dlmread(), you can use surf() like I showed, or scatter() or imagesc() like Adam showed, or even histogram() or histogram2(), depending on what you mean by density. Still even now, no one has a clear idea of what you mean by that, other than your acceptances of Adam's answer which I guess means you wanted either scatter() or imagesc().
Más respuestas (1)
Adam Danz
el 19 de Sept. de 2018
Editada: Adam Danz
el 19 de Sept. de 2018
You can read the data back in with dmlread()
data = dlmread('data.txt', '%f');
' data' will be the [10000 x 3] matrix.
For the figure, I'm not sure if this is what you're looking for but you can try it.
figure;
imagesc(data(:,1), data(:,2), data(:,3));
colorbar
Another option
figure;
scatter(data(:,1), data(:,2), 10, data(:,3))
1 comentario
Adam Danz
el 19 de Sept. de 2018
See comments under the answer provided by @ImageAnalyst for more interpretations of what you'd like to plot in 2D space.
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