Plot 3D surface from Excel .csv File

Hello,

I am trying to plot 3D surface from the attached excel csv file (data.csv).

I want the surface to be smooth if possible.

• x = first column;
• y = second column;
• z = third column.

I am new to Matlab and I have been struggling to do it. Could you please help me?

Also, how could I annotate the minumum of the surface and its x and y coordinates as well.

Thanks a lot!

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Answer 1

[Simon Chan]

You may extract the data using function readmatrix.

clear; clc;
rawdata = readmatrix('data.csv');
x = reshape(rawdata(:,1),[],51);                % Reshape the column matrix into 51 columns
y = reshape(rawdata(:,2),[],51);
z = reshape(rawdata(:,3),[],51);
surf(x,y,z)

result as follows:

[HAMID]

thanks a lot! is there a way to annotate the minimum point?

[Simon Chan]

Minimum points with red marker. Or you would like to annotate with text?

clear; clc;
rawdata = readmatrix('data.csv');
x = reshape(rawdata(:,1),[],51);                % Reshape the column matrix into 51 columns
y = reshape(rawdata(:,2),[],51);
z = reshape(rawdata(:,3),[],51);
surf(x,y,z)
minvalue = min(min(z));                         % Find the minimum value
[row,col] = find(z==minvalue);                  % Find the location of minimum points
surf(x,y,z,'FaceAlpha',0.5,'EdgeColor','none')
hold on
plot3(x(row,col),y(row,col),z(row,col),'r*','MarkerSize',10);   % Plot the red markers
xlabel('x-axis')                                                % Labels (you may modify)
ylabel('y-axis')
zlabel('Potential Energy')

[HAMID]

Thanks a lot! this is perfect and I now see how you calculated the minimum value and its corresponding coordinates! thans again.

[Simon Chan]

Sure.

The minimum vlaue is stored in variable 'minvalue', you may type this variable name in Command Window and then gives the answer. In your case 234.55.

The x and y coordinates are stored in variable 'row' and 'col', again type these name in the Command Window and you can get row = 26 & 26 and col = 20 & 21. Hence there are 2 minimum points located on row #26 and column #20 & #21.

If you want to get back the value of x and y in these corrdinates, type x(row, col) and y(row,col) and in this case, the value of x is 0.25, while value of y are 0.19 & 0.20.

On the other hand, type z(row,col) can give you the minimum value as well.

[HAMID]

I really appreciate. I got a better understanding of how Matlab works from your answers as well. Thanks!

[Tom]

hi, i'm trying to use this code to create my own contour plot from a csv file that has data in a 3x55 matrix.

is there any reason you converted the column matrix into specifically a 51 column matrix?

and how would i need to adapt this code to use with my csv file?

sorry, i am also very new to matlab but it's the only software i have access to that does what i need for a final year project.

thanks, t

[Simon Chan]

You may spend some time to look at the attached csv file.

Actually there are totally 51x51 data but arranged in a column vector. On the other hand, function surf requires z-coordinates to be a matrix. So the conversion mainly converts the z-coordinates, which is the third column in this csv file into a matrix.

While for the x and y coordinates, they are both going from 0 to 0.5 with step size 0.01, and hence there are totally 51 data points. Without extracting the x and y-coordinates from the csv file, you may also use the following line to do the same thing.

[x,y] = meshgrid(0:0.01:0.5);                                       % 2D grid for both 0:0.05:0.5
z = reshape(rawdata(:,3),length(0:0.01:0.5),length(0:0.01:0.5));    % Reshape z into a 51x51 matrix
surf(x,y,z);