MATLAB Answers

Create one file from many files

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Ivan Mich
Ivan Mich on 22 May 2020
Edited: Stephen Cobeldick on 2 Jun 2020
Hello,
I have multiple files, with the following names:
m1,m2,....., m25 (files without extension).
Each file has a number. I would like to create a file which will have all the values vertically of each file I have.
I am importing the files I have and the file I would like to create.
Thank you in advance

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Answers (2)

Cristian Garcia Milan
Cristian Garcia Milan on 22 May 2020
Hi!
You should use
fid = fopen(file(i),'r');
for each file. Then read it. I usually use
value(i) = str2num(char(fread(fid)));
Then you can close the file
fclose(fid);
If you want to write it in a file, you shoul follow a similar way.
fid = fopen(file_to_write,'w');
fprintf(fid,'%f\n',value);
fclose(fid)
Hope it helps!

  3 Comments

Ivan Mich
Ivan Mich on 22 May 2020
command window shows me:
Undefined function or variable 'file'.
Cristian Garcia Milan
Cristian Garcia Milan on 22 May 2020
try the following code:
files = dir('m*.');
values = zeros(1,length(files));
for i = 1:length(files)
file = files(i).name;
fid = fopen(file,'r');
values(i) = str2num(char(fread(fid)));
fclose(fid);
end
fid = fopen('OutputFile','w');
fprintf(fid,'%f\n',values);
fclose(fid)
Stephen Cobeldick
Stephen Cobeldick on 22 May 2020
Warning: the code given in the previous comment will not parse the filenames in alphanumeric order. With the filenames given in the original question, that code will parse the files and concatenate the data in this order:
m1
m10
m11
...
m19
m2
m20
m21
...
m25

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Stephen Cobeldick
Stephen Cobeldick on 22 May 2020
Edited: Stephen Cobeldick on 22 May 2020
D = 'absolute/relative path to where the files are saved';
N = 25; % number of files
C = cell(1,N);
for k = 1:N
F = fullfile(D,sprintf('m%u.txt',k));
C{k} = dlmread(F);
end
M = vertcat(C{:});
dlmwrite('final.txt',M,'\t')
See also:

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Ivan Mich
Ivan Mich on 1 Jun 2020
I mean something is going wrong with the loop:
for n=1:numel(st);
for i=1:size(nam);
FP=fopen(sprintf('m%g0.txt',i),'wt');
fprintf(FP,'%s\t',num2str(Results));
fclose(FP);
D = 'absolute/relative path to where the files are saved';
N = 25; % number of files
C = cell(1,N);
for k = 1:N
F = fullfile(D,sprintf('m%u.txt',k));
C{k} = dlmread(F);
end
M = vertcat(C{:});
FF = sprintf('final%u.txt',n);
dlmwrite(FF,M,'\t')
end
end
Ivan Mich
Ivan Mich on 1 Jun 2020
Excuse me, How could I replace in my code dlmwrite with writematrix?
Sorry to ask you again and again but I am really confused!
Stephen Cobeldick
Stephen Cobeldick on 1 Jun 2020
I posted before refreshing this page, so I did not see your comment with code. On the first iteration the outer two loops your code has only created one file, but the nested loop that you added attempts to read twenty-five files, of which twenty-four don't exist. I don't see how that could work.
Get rid of the innermost loop by merging its code in with the outer two loops:
D = 'absolute/relative path to where the files are saved'; % you need to change this!
for ii = 1:numel(st);
N = size(nam,1); % or move to before the loops.
C = cell(1,N);
for jj = 1:N;
fnm = fullfile(D,sprintf('m%g0.txt',jj));
[fid,msg] = fopen(fnm,'wt');
assert(fid>=3,msg)
fprintf(fid,'%s\t',num2str(Results));
fclose(fid);
%
C{k} = dlmread(fnm);
end
mat = vertcat(C{:});
fnm = fullfile(D,sprintf('final%u.txt',ii));
dlmwrite(fnm,mat,'\t')
end
Are all of the separate number files really required? Why not just concatenate the data directly in MATLAB memory and only save the final file?

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