read data to plot

Hello, I'm trying to read the data in the zip file attached with this code but I'm getting errors, not sure how I could plot the data contained in this file? any help will be greatly appreciated. Thanks

clear;
clc;

nx=225;ny=66;nfields=9;

a=readmatrix('NACA4612_1E-4_225x66.XYZ_M=0.5_ALPHA_2.0_Turbulent.dat','Headerlines',5)';

b=reshape(a(1:nx*ny*2),[nx,ny,2]);

x=b(:,:,1);y=b(:,:,2);

%centroids (improve this by averaging the 4 corners)

xc=x(1:end-1,1:end-1)+diff(x(:,1:end-1))/2 +diff(x(1:end-1,:),[],2)/2;

yc=y(1:end-1,1:end-1)+diff(y(:,1:end-1))/2 +diff(y(1:end-1,:),[],2)/2;

b=reshape(a(nx*ny*2+1:end),[nx-1,ny-1,nfields]);%nine dependent variables

%plot pressure

figure;surf(xc,yc,b(:,:,4));

view(2);shading flat;axis image;axis([-1,1,-1,1])

[Star Strider]

MATLAB R2023a has not problem reading it, however there does not appear to be much to see in the plot —

Uz = unzip('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1370564/NACA4512_1E-4_225x66.XYZ_M=0.5_ALPHA_2.0_TURBULENT.dat.zip');
a = readmatrix(Uz{1})

a = 16074×10

0.5011 0.5011 0.5010 0.5010 0.5009 0.5008 0.5007 0.5006 0.5005 0.5003 0.5002 0.5000 0.4998 0.4997 0.4995 0.4993 0.4991 0.4989 0.4986 0.4983 0.4979 0.4975 0.4970 0.4964 0.4958 0.4950 0.4942 0.4932 0.4920 0.4908 0.4893 0.4876 0.4856 0.4834 0.4808 0.4779 0.4746 0.4708 0.4664 0.4615 0.4559 0.4495 0.4422 0.4340 0.4248 0.4144 0.4027 0.3897 0.3751 0.3590 0.3412 0.3216 0.3002 0.2770 0.2519 0.2251 0.1965 0.1664 0.1348 0.1022 0.0686 0.0344 0 -0.0344 -0.0684 -0.1017 -0.1341 -0.1653 -0.1950 -0.2232 -0.2496 -0.2743 -0.2972 -0.3183 -0.3376 -0.3552 -0.3712 -0.3856 -0.3986 -0.4103 -0.4207 -0.4300 -0.4382 -0.4456 -0.4521 -0.4578 -0.4629 -0.4674 -0.4714 -0.4749 -0.4779 -0.4807 -0.4831 -0.4852 -0.4870 -0.4886 -0.4901 -0.4913 -0.4925 -0.4935

% clear;
% clc;

nx=225;
ny=66;
nfields=9;

% a=readmatrix('NACA4612_1E-4_225x66.XYZ_M=0.5_ALPHA_2.0_Turbulent.dat','Headerlines',5)';

b=reshape(a(1:nx*ny*2),[nx,ny,2]);

x=b(:,:,1);
y=b(:,:,2);

%centroids (improve this by averaging the 4 corners)

xc=x(1:end-1,1:end-1)+diff(x(:,1:end-1))/2 +diff(x(1:end-1,:),[],2)/2;

yc=y(1:end-1,1:end-1)+diff(y(:,1:end-1))/2 +diff(y(1:end-1,:),[],2)/2;

b=reshape(a(nx*ny*2+1:end),[nx-1,ny-1,nfields]);%nine dependent variables

bSz = size(b)

bSz = 1×3

224 65 9

%plot pressure

figure
surf(xc,yc,b(:,:,4))
view(2)
shading flat
axis image
axis([-1,1,-1,1])

.

[Cesar Cardenas]

thanks I can visualize it better now. However, for this case I'm gettng this error, not sure how to fix it.?? Any help will be appreciated. thanks

b=reshape(a(1:nx*ny*2),[nx,ny,2]);
x=b(:,:,1);
y=b(:,:,2);
%centroids (improve this by averaging the 4 corners)
xc=x(1:end-1,1:end-1)+diff(x(:,1:end-1))/2 +diff(x(1:end-1,:),[],2)/2;
yc=y(1:end-1,1:end-1)+diff(y(:,1:end-1))/2 +diff(y(1:end-1,:),[],2)/2;
b=reshape(a(nx*ny*2+1:end),[nx-1,ny-1,nfields]);%nine dependent variables
bSz = size(b)
Error using reshape
Number of elements must not change. Use [] as one of the size inputs to automatically calculate the appropriate size for
that dimension.
 
xc=x(1:end-1,1:end-1)+diff(x(:,1:end-1))/2 +diff(x(1:end-1,:),[],2)/2;
yc=y(1:end-1,1:end-1)+diff(y(:,1:end-1))/2 +diff(y(1:end-1,:),[],2)/2;
b=reshape(a(nx*ny*2+1:end),[nx-1,ny-1,nfields]);%nine dependent variables
Error using reshape
Number of elements must not change. Use [] as one of the size inputs to automatically calculate the appropriate size for
that dimension.

[Cris LaPierre]

Just work out the math. The number of elements in a(nx*ny*2+1:end) is not the same as the number of elements in [nx-1,ny-1,nfields].

[Cesar Cardenas]

Thanks, I've been trying that, but I have not been able to figure it out. can you give me a bit more detail? Thanks

[Cris LaPierre]

Sure. Can you provide the values of nx, ny, and nfields at this point in your code?

Answer 1

[Debraj Maji]

Hi @Cesar Cardenas

I see that you are trying to read data form a file with a .DAT extension. I have downloaded the zip file shared and upon inspection have found that there is a mismatch in the file name used for reading the file. You can find the required correction below:

a=readmatrix('NACA4512_1E-4_225x66.XYZ_M=0.5_ALPHA_2.0_TURBULENT.dat','Headerlines',5)';   

The corresponding figure obtained using the shared data is attached below:

Make sure to add the path for the data file is added before the script is run.

I hope this helps!