Drawing a segment of a cylinder from a matrix

Question

Yvotte Brits 2017-9-6

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https://ww2.mathworks.cn/matlabcentral/answers/355424-drawing-a-segment-of-a-cylinder-from-a-matrix

评论： Yvotte Brits 2017-9-14

3d Fluxes.xls

Hi, I want to do a 3d plot of a 1/9th slice of a cylinder of the attached data points in Matlab. There is 51 layers in the z-direction, 36 points in the r direction and 9 points in the theta direction. Every coordinate have a value in matrix form that have to be indicated as a color in the 1/9th slice of the cylinder. What is the best way to draw this matrix in a 3d plot in Matlab?

Regards

Yvotte

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Stephen23 2017-9-13

编辑：Stephen23 2017-9-13

Yvotte Brits' "Answer" moved here:

Hi I want to show the (r,theta,z) geometry of the sliced cylinder(1/9th sliced of the cylinder), and then the values flux as a color. So it is basically a 4d representation, with the r,theta and z being the coordinates of the sliced cylinder and then the values (flux) being represented as color etc.

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Answer 1

Jocie Kluger 2017-9-14

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https://ww2.mathworks.cn/matlabcentral/answers/355424-drawing-a-segment-of-a-cylinder-from-a-matrix#answer_281566

编辑：Jocie Kluger 2017-9-14

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The general idea is to reshape the z, r, and theta coordinates into 2D matrices of size (53*37) x 9 that correspond to the color data. Then, transform the r and theta coordinates into Cartesian coordinates. Transform all of the matrices into vectors so that they can be plotted with the scatter3 command, where you can specify each marker color. Please refer to the documentation for details on the command syntax.

    %Read and format data
    filename = '3d Fluxes.xls';
    sheet= 1;
    z= xlsread(filename,sheet,'A:A'); %get z data
        z(isnan(z))= []; %remove NaN
    r= xlsread(filename,sheet,'B:B'); %Get r data
        r(isnan(r))= [];
    theta= xlsread(filename,sheet,'C2:K2'); %Get theta data
    ColorData= xlsread(filename,sheet,'C1:K2067');
    %Remove extraneous rows. Not most efficient way
    removeRowInds= 1; %first row to remove. Excel merge in row 2 affects this.
    for i= 1:52
        removeRowInds= [removeRowInds 39*i 1+39*i];
    end
    ColorData(removeRowInds,:)= [];
    ColorVector= reshape(ColorData, numel(ColorData), 1);
    %%Reformat data so all 1D vectors.
    %Order to take data: 37*53 rows. Then reshape column-wise. 
    %zVector should repeat r times theta times then change value
    zRow= z'; %turn z into row vector
    zMat1= repmat(zRow, 37, 1);
    zVector1= reshape(zMat1, numel(zMat1),1);
    zMat= repmat(zVector1, 1,9); %z value for each ColorData value
    zVector= reshape(zMat,numel(zMat), 1); %turn z back into a vector
    rMat= repmat(r, 1, length(theta));
    rVector= reshape(rMat, numel(rMat), 1);
    thetaMat= repmat(theta, 37*53,1);
    thetaVector= reshape(thetaMat, numel(thetaMat),1);
    %Turn r and theta into matrices of X and Y
    X= rVector.*cos(thetaVector);
    Y= rVector.*sin(thetaVector);
    %%Final plot
    S = repmat(25,numel(X),1); %Specify marker size
    scatter3(X,Y,zVector, S, ColorVector);% scatter3(X,Y,Z,S,C)