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2D color or surface plot based on 3 vectors of data

Asked by Jordi Riba on 11 Apr 2018
Latest activity Commented on by Jordi Riba on 12 Apr 2018
I want to do a 2D plot based on 3 vectors of data (X,Y and Z) coming from rig results, in order to have some color surfaces between the points that shows the trend to where the values are increasing or decreasing. Ideally should contain also some iso-lines appart from the Colors. Not sure how to achieve it but I have seen it published.
The closest I could get to what I want was to use a simple scatter (X,Y Z) plot. But when I tried to generate surfaces between them by using the ‘peaks’ function then I had the problem that my X and Y plots are not strictly increasing or decreasing, and that there were some repeated values, so I could not use the function ‘contourf’.
Any help is more than welcome!

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2 Answers

Answer by Pawel Jastrzebski on 11 Apr 2018
Edited by Pawel Jastrzebski on 11 Apr 2018
 Accepted Answer

How about this:
% interpolation data
% as in:
% https://uk.mathworks.com/help/matlab/ref/scatteredinterpolant.html?searchHighlight=scatteredInterpolant&s_tid=doc_srchtitle#responsive_offcanvas
F = scatteredInterpolant(datarig.X,datarig.Y,datarig.Z);
[xq,yq] = meshgrid(40:115,25:65);
F.Method = 'natural';
zq = F(xq,yq);
%colorbar data
limLow = min(datarig.Z);
limHi = max(datarig.Z);
c = linspace(limLow,limHi,length(datarig.Z));
figure;
scatter3(datarig.X,datarig.Y,datarig.Z,[],c);
caxis([limLow, limHi])
colorbar('Limits',[limLow, limHi]);
hold on;
contourf(xq,yq,zq)
%surface(xq,yq,zq)
%view(90,90)
Output:

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Show 1 older comment
Hi Pawel, that is very good !!! Thanks! Which view orientation should I take to only see the bottom part , and not the top? Thanks again !!!
Plot only the:
figure;
contourf(xq,yq,zq)
And nothing else. I added the other plots to see how the interpolation really worked.
Thanks Pawel!!! it works really well !!! Cheers! Jordi

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Answer by Pawel Jastrzebski on 11 Apr 2018

In order to be able to use contour plot, your Z data need to be of X*Y size. What you can do is the following:
% C is a matrix of colours assigned to your data
% Color will get assigned based on the user specified condition
% Simple example with 3 colors RGB
% Red = [1 0 0]
% Green = [0 1 0]
% Blue = [0 0 1]
c = zeros(size(datarig,1),3);
cond1 = datarig.Z<=1.0e+09 *1;
c(cond1,1) = 1;
cond2 = (datarig.Z>1.0e+09 *1) & (datarig.Z<=1.0e+09 *1.15);
c(cond2,2) = 1;
cond3 = ~(cond1+cond2);
c(cond3,3) = 1;
% point size
s = 25;
figure
scatter3(datarig.X,datarig.Y,datarig.Z,s,c)
view(90,90)
To obtain something like:

  1 Comment

Thanks Pawel, but this is not what I wanted. To get something similar I could just simple use a scatter, and I get what is shown on the attachment. I want to create extrapolated surfaces with iso-lines.

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