Dot indexing is not supported for variables of this type in a for loop

Hello everyone,

I am trying to execute this code and I am having the following error:

clc;clear;close all

addpath('/media/hf9098/easystore/MATLAB/POD')

SnapshotsAddress = pwd; % put current path here

files = dir(fullfile(SnapshotsAddress,'data_*.txt'));

n_snapshots = natsortfiles(files);

if iscell(n_snapshots) == 0;

n_snapshots = (n_snapshots);

end

n_snapshots = size(files,1);

for j = 1:numel(n_snapshots)

folder = n_snapshots(j).folder;

filename = n_snapshots(j).name;

fid = fullfile(n_snapshots(j).folder,n_snapshots(j).name);

data = dlmread(fid);

x = data(1,:) % x coordinate

y = data(2,:) % y coordinate

U(j,:) = data(4,:); % u velocity

V(j,:) = data(5,:); % v velocity

end

%Section 2 -­‐ Compute spatial correlation matrix C

c1 = U*U';

c2 = V*V';

C = (c1+c2)/n_snapshots;

%Section 3 -­‐ Solve the eigenvalue problem: C * EigenVector = EigenValue * EigenVector

[beta, lmd] = svd(C);

%Section 4 -­‐ Calculate basis functions

phix = U'*beta;

phiy = V'*beta;

% Normalize basis functions

GridNum = size(x,2);

for j=1:n_snapshots

PhiNor = 0;

for i=1:GridNum

PhiNor = PhiNor + phix(i,j)^2 + phiy(i,j)^2;

end

PhiNor = sqrt(PhiNor);

phix(:,j)= phix(:,j)/PhiNor;

phiy(:,j)= phiy(:,j)/PhiNor;

end

%Section 5 -­‐ Calculate coefficient

TimCoeU = U*phix;

TimCoeV = V*phiy;

TimCoe = TimCoeU + TimCoeV;

%Section 6 -­‐ Export basis functions

for a=1:n_snapshots

FilNamPhi = 1000+a;

PhiOut = fopen([SnapshotsAddress,num2str(FilNamPhi),'.txt']', 'wt');

fprintf(PhiOut, '#DaVis 7.2.2 2D-­‐vector 16 145 145 "position" "mm" "position" "mm" "velocity" "m/s"\n');

phia = [x;y;phix(:,a)';phiy(:,a)'];

fprintf(PhiOut, '%20.9f %20.9f %20.9f %20.9f\n',phia);

fclose(PhiOut);

end

% Write coefficients into excel file

xlswrite([SnapshotsAddress,'TimCoe.xlsx'],TimCoe);

The error is:

Dot indexing is not supported for variables of this type.

Error in VelocityDistributionPOD (line 57)

folder = n_snapshots(j).folder;

Even upon commenting line57, it is still present in line58 and line59

Any thoughts how to override such error?

Thank you!

Answer 1

[Steven Lord]

First:

n_snapshots = natsortfiles(files);

n_snapshots was a struct array. But then:

if iscell(n_snapshots) == 0;
    n_snapshots = (n_snapshots);
end
n_snapshots = size(files,1);

you changed it to a scalar double. Change one of the variable names to something more indicative of its purpose.