Octave: read multiple files from a directory in an iterative way using variable filename

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My directory contains 2550 text files. I want to read these files as separate array elements of the cell array file_contents. Reading one file at a time is easy i.e. 1.txt into file_contents{1} and so on. I want to create a loop that will read all these files into respective element of the file_contents cell array.

What I have tried:

The code I tried:

file_contents = {};

for i = 1:2551
    file_contents{i} = readFile('%d.txt', i);
end

Running the above code gives me the error:

error: fscanf: invalid stream number = -1

Here is the readFile function I am using:

function file_contents = readFile(filename)

fid = fopen(filename);
if fid
    file_contents = fscanf(fid, '%c', inf);
    fclose(fid);
else
    file_contents = '';
    fprintf('Unable to open %s\n', filename);
end

end

Posted 8-Jan-17 1:13am

Pratham Solanki

Updated 8-Jan-17 2:05am

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Patrice T 8-Jan-17 7:24am

And you have a question ?
Describe the problem.

Pratham Solanki 8-Jan-17 7:27am

How do I read the multiple files as I intend to because the code I am trying is giving me the error I mentioned.

3 solutions

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Richard MacCutchan · Answer 1 · 2017-01-08T01:49:00

C++

file_contents{i} = readFile('%d.txt', i);

You are passing two parameters to the readFile function, but it only accepts the first one. So when you try to call fopen('%d.txt'); there is no such file, and the function returns -1. You then call fscanf(-1, ...) which fails as there is no such open file stream.

You need to change your readFile function to accept both parameters, and combine them to form a valid file name. You also need to check the value returned from fopen is not equal to -1, which indicates an error.

Peter Leow · Answer 2 · 2017-01-08T01:56:00

You are calling a function

readFile('%d.txt', i)

with 2 arguments, and that function is

function file_contents = readFile(filename)

.Notice any thing amiss?
+++++{round 2]+++++

Quote:
Yes! I am passing 2 arguments while the function only accepts 1.
Any suggestions as to how I may resolve it?

Are you kidding? It is your code, your function. First, ask yourself, what purposes those 2 arguments are, if they are really needed for the function to do the job, then add one more argument to the readfile() function, otherwise, get rid of the redundant one from the calling function. This is very basic.
Getting code from somewhere and hoping it to work out-of-the-box is getting you nowhere. The correct way is to read up on the relevant documentation and do it correctly:
1. Function Basics - MATLAB & Simulink[^]
2. Read data from text file - MATLAB fscanf[^]
2. Loop Control Statements - MATLAB & Simulink[^]

Patrice T · Answer 3 · 2017-01-08T02:05:00

Solution 3

You get the error because fopen(filename); fails and it fails because '%d.txt' do not magically transform to a filename.

Posted 8-Jan-17 2:05am

Patrice T

Octave: read multiple files from a directory in an iterative way using variable filename

3 solutions

Solution 1

Solution 2

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