MATLAB: Color-coding a 2D plot

2d colour plot

Hi everyone! I want to make a nice colour graph with my data but I don't know exactly what I'm looking for. So in my experiment, I measured the excess pore pressure in 12 different positions in a deposit of sand (40x40cm side view). I have an example of the results I have for the transducers 9, 10, 11 and 12 (Fig.1). What I want is an easy way to visualise this changes in pressure in all transducers at once through time. For example, a square 40x40cm and the changes in colour (pressure) for each transducer area for the first 2 minutes (Fig.2). I know the exact position of each transducer: 12cm between them and 2cm from the top/bottom. Basically I want 2min "video" to see which part of the sand deposit is contracting or dilating during the experiment. I'm new in MatLab. I only know the basic codes to analyse my data. But now I have other ideas to present this data. Can you help me please? Thanks! Joana

Best Answer

The simplest way to create an animation is to first create a plot and then update the 'XData', 'YData' and 'ZData' properties (or in this case just the 'ZData'). You can spend days adjusting the visuals. This code provides the basics for plotting values over time in a 4x3 grid. I hope this is somewhat what you had in mind. Happy to help further if it's not.

Note: You did not give me the variable S, so I could not adjust the data accordingly. I just used the data you gave me.

DenseSand = fileread('D.Test.lvm');
Densesant = strrep(DenseSand,',','.');
DenseSand = str2num(DenseSand);
%%Data
Num_Samples2 = [1:1:size(DenseSand,1)]';
MeasFr = 200;
Time2 = Num_Samples2 / MeasFr;
T=DenseSand.*0.1;
z=T(:,[4 5 9 2 6 10 3 7 11 4 8 12]);
%%Coordinates
x=repmat(2:12:26,1,4);
y=repmat(2:12:38,3,1);
y=y(:);x=x(:);
%%Create finer mesh
[Xq,Yq]=meshgrid(0:1:40,0:1:40);
%%Plot
h=surf(Xq,Yq,zeros(size(Xq)));
set(gca,'ZLim',[0 1e5])
colormap('jet')
view(2)
%%Interpolate and plot each frame
for i=1:length(Time2)
h.ZData=griddata(x,y,z(i,:)',Xq,Yq,'nearest');
drawnow
title(['Time: ',num2str(Time2(i))])
end

This code takes more than 2 minutes to run on my machine. It's easy to increase the time between animations by inserting a pause, however the minimum time can only be changed by making the code more efficient. You can however increase the amount of frames by not plotting every value, simply change the iterations to

i:step:length(Time2)

Related Solutions

MATLAB: How to speed up an animation plot

Use the profiler to find the bottleneck of the code. It is not worth to improve a part, which takes 1% of the runtime, because an (impossible) infinite acceleration would reduce the runtime by 1% only.

Move repeated operations out of the loop, e.g.:

h = linspace(103.6,104,30);
y = linspace(1.5,1.25,30);   
[X,Y] = meshgrid(h,y);

Replace the loops of i and j by:

V = zeros(30, 30);
for iC = 1:900
  if ~isempty(cellArray{i,j})
    V(iC) = cellArray{i,j}(k);
  end
end

But the main problem is (most likely - I cannot run your code) that a huge bunch of SURF objects is created. Prefer to create one object only and adjust its values. Define "hSurf = []" before the loops. Then:

% Replace:
% surf(Xq,Yq,Vq); % plots interpolated data
% By:
if isempty(hSurf)
  hSurf = surf(Xq,Yq,Vq); % plots interpolated data
else
  set(hSirf, 'XData', Xq, 'YData', Yq, 'ZData', Vq);
end

Matlab's 1D interpolation is really lame. I don't know if this matters interp2 also. But if it does, think of replacing it by a handmade function. X,Y,Xq and Vq are constant in your problem. This should be useful for creating a faster version.

For more details it would be useful if you provide input data. It is hard to guess, where improvements of the code are useful, without running the code. It is like repairing a car without starting the engine.

MATLAB: 3D density plot – multiple isosurfaces on the same plot

I found it. This how I did the attached image:

      figure
      quantum=max(nfe)/8;
      isovalue=6*quantum;
      surf1=isosurface(x,y,z,normalized_Free_Energy_map,isovalue);
      p1 = patch(surf1);
      isonormals(x,y,z,normalized_Free_Energy_map,p1);
      set(p1,'FaceColor','red','EdgeColor','none','FaceAlpha',0.1); % set the color, mesh and transparency level of the surface
      daspect([1,1,1])
      view(3); axis tight
      camlight; lighting gouraud
      isovalue=4*quantum;
      surf2=isosurface(x,y,z,normalized_Free_Energy_map,isovalue);
      p2 = patch(surf2);
      isonormals(x,y,z,normalized_Free_Energy_map,p2);
      set(p2,'FaceColor','yellow','EdgeColor','none','FaceAlpha',0.2);
      isovalue=2*quantum;
      surf3=isosurface(x,y,z,normalized_Free_Energy_map,isovalue);
      p3 = patch(surf3);
      isonormals(x,y,z,normalized_Free_Energy_map,p3);
      set(p3,'FaceColor','cyan','EdgeColor','none','FaceAlpha',0.3);
      isovalue=quantum;
      surf4=isosurface(x,y,z,normalized_Free_Energy_map,isovalue);
      p4 = patch(surf4);
      isonormals(x,y,z,normalized_Free_Energy_map,p4);
      set(p4,'FaceColor','blue','EdgeColor','none','FaceAlpha',1);

Best Answer

Related Solutions

MATLAB: How to speed up an animation plot

MATLAB: 3D density plot – multiple isosurfaces on the same plot

Related Question