Read number from a string from multiple files

Hello,

I have multiples output files from a numerical simulations called eta_0000d, where d is a number going from 0 to #of iteration.

I am trying to make a code which will put all the eta_0000d files into a structure for further analysis.

So far this is the code I made:

fdir = './output/';

%Load eta output

n = 400

S = [];

for i = 1:n

if i<=9

filename = sprintf('eta_0000%d',i);

elseif i<100

filename = sprintf('eta_000%d',i);

else

filename = sprintf('eta_00%d',i);

end

S(i).eta = load([fdir filename]);

end

In the code I manually put the number n (n=400) equivalent to the total output eta files that I see in the output folder. Is there a way to modify my code such that it counts how many eta files there are in the output folder without having to manually input this value?

Thank you

[Stephen23]

Note that you should replace this:

if i<=9
    filename = sprintf('eta_0000%d',i);
elseif i<100
    filename = sprintf('eta_000%d',i);
else
    filename = sprintf('eta_00%d',i);
end

with one SPRINTF call, by specifying the fieldwidth and leading zero:

filename = sprintf('eta_%05d',i);
%                        ^   leading zeros
%                         ^  field width

See: https://www.mathworks.com/help/matlab/ref/sprintf.html#btf_bfy-1_sep_shared-formatSpec

And also replace the text concatenation with FULLFILE.

Answer 1

[Stephen23]

"is there a way to modify my code such that it counts how many eta files there are in the output folder without having to manually input this value?"

Of course, just use DIR:

https://www.mathworks.com/help/matlab/ref/dir.html

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

For example:

P = './output';
S = dir(fullfile(P,'eta_*'));
for k = 1:numel(S)
    F = fullfile(P,S(k).name);
    S(k).eta = load(F);
end

If the files are actually text files, then you should use a more appropriate function, e.g.:

https://www.mathworks.com/help/matlab/ref/readmatrix.html

[carola forlini]

Thank you for the help!