Error: "filename" must be a string scalar or character vector.

I am trying to sort of creat an animation of a bunch of text files. The thing is, these text files are techically 3D matrices collapsed as 2D matrix and then I am reshaping them back to 3D to plot.

The code:

upperDir = 'C:\Users\J\Desktop\Folder\';
subDir = {'DataFile\'};  
Frame = 161; %number of text files

Nx = 64; 
Ny =64;  
Nz = 64; 

Lx =128; 
Ly = 128;  
Lz = 128; 

x   = (0:Nx-1)/Nx*2*pi;          
y   = (0:Ny-1)/Ny*2*pi;
z   = (0:Nz-1)/Nz*2*pi;
dx = Lx/Nx;
dy = Ly/Ny;
dz = Lz/Nz;
[X,Y,Z] = meshgrid(x,y,z);

for i = 1:Frame 
    %Test=reshape(readmatrix('Test161.txt'),64,64,64); 
    Test = reshape(readmatrix([upperDir  subDir 'n' num2str(i) '.txt']),64,64,64); %error here
    figure
    isosurface(X,Y,Z,Test);
    shading flat;
    grid on;
    xlabel('x(m)'); ylabel('y(m)'); zlabel('z(m)'); 

 
end

The error:

Error using readmatrix (line 157)
"filename" must be a string scalar or character vector.

Error in PlasmaCloud3DFourier (line 351)
    Test = reshape(readmatrix([upperDir  subDir 'n' num2str(i) '.txt']),64,64,64);

Answer 1

[KSSV]

Change this line

[upperDir  subDir 'n' num2str(i) '.txt']

to

[upperDir,filesep,subDir,filesep,'n',num2str(i),'.txt']

Also have a look on dir. Here you can extract the required text files and make your required path using fullfile

[Jamie Al]

Sorry, what is filesep here?. Unfortunately, I am getting the same error.

Answer 2

[VBBV]

subDir = 'DataFile\';

Change this line as above.

[VBBV]

It seems you are using cell character