Data Reshape for Contour Plot

Hello,

I'm facing a few problems while data reshaping. I have velocity values in a cartesian coordinate system (x,y,z) . The values are at the surface of a cylinder with a defined radius.

Therefore a transformation into cylinder coordinates to plot the data as 2D contour (Angle and Height) is suitable.

My Problem is that I have all the necessary data in the file 'TransformedData.txt' but it is not the required format for contourf.

I tried to reshape the data inspired by this post: (https://de.mathworks.com/matlabcentral/answers/421043-contour-plot-based-on-xyz-data) but it's still not working.

clc,close all
clearvars


filename='RawDataCFXPost.xlsx';

% Data Transformation
x=xlsread(filename,'A3:A36003');% Cartesian Coordinate x
y=xlsread(filename,'B3:B36003');% Cartesian Coordinate y
z=xlsread(filename,'C3:C36003');% Cartesian Coordinate z
ZData=xlsread(filename,'D3:D36003');% Velocity Value v
[theta,rho,z] = cart2pol(x,y,z);% Coordinate Transformation from Cartesian to Clyinder Coordinate System
A=[theta,rho,z,ZData];% Array with Transformed Data

writematrix(A,'TransformedData.txt','Delimiter',' ');  
type TransformedData.txt;

% Data Reshape
Data = load('TransformedData.txt');
[Du,D1] = unique(Data(:,1));
Dd = diff(D1);
DataNew = reshape(Data, Dd(1), [], size(Data,2));
Angle = DataNew(:,:,1);
Height = DataNew(:,:,3);
Velocity = DataNew(:,:,4);

% Contour Plot
figure
contourf(Angle, Height, Velocity)

Maybe someone has a clue to solve this issue.

With best regards

Steffen

Answer 1

[KSSV]

T = readtable('https://in.mathworks.com/matlabcentral/answers/uploaded_files/1776380/RawDataCFXPost.xlsx');
[theta,rho,z] = cart2pol(T.(1),T.(2),T.(3));

x = linspace(min(theta),max(theta),500) ; 
y = linspace(min(rho),max(rho),500) ; 
z = T.(4) ; 
[X,Y] = meshgrid(x,y) ; 
Z = griddata(theta,rho,z,X,Y) ; 

Warning: Duplicate data points have been detected and removed - corresponding values have been averaged.

contourf(X,Y,Z)

[KSSV]

But I would prefer:

T = readtable('https://in.mathworks.com/matlabcentral/answers/uploaded_files/1776380/RawDataCFXPost.xlsx');
scatter3(T.(1),T.(2),T.(3),[],T.(4),'filled')

[Steffen B.]

Hello KSSV,

thankls for your answer. I did a few adaptions and now it's working just fine.

Thanks for your help.

[KSSV]

That's great...cheers :)