Read data from file into arrays matlab

Question

I was not sure which title fits better in my case so I just left it to be written in the most general way. I have the file with following structure:

Step 1
0.10190103    
0.10145140    
0.10097524    
0.10050153    
0.10003042    
9.95795131E-02
9.91610140E-02
Step 2
9.81189385E-02
9.75561813E-02
9.80424136E-02
0.10000000    
0.10000000    
9.80617628E-02
9.77829769E-02
...
Step N
0.10000000    
0.10000000    
9.93788019E-02
0.11977901    
0.12290157    
0.12588248    
0.12861508

And I need to read it from N arrays, so

V1 = [0.10190103    
0.10145140    
0.10097524    
0.10050153    
0.10003042    
9.95795131E-02
9.91610140E-02]

V2 = [9.81189385E-02
9.75561813E-02
9.80424136E-02
0.10000000    
0.10000000    
9.80617628E-02
9.77829769E-02]

VN = [0.10000000    
0.10000000    
9.93788019E-02
0.11977901    
0.12290157    
0.12588248    
0.12861508]

I have read some examples to read data into arrays, but have not got something related to my case...

Can someone help me please..?

My Try

d = readtable('whole res.txt'); % name of file 
d = table2cell(d);  
d = regexprep(d,' ','');
d = cellfun(@str2double,d,'uni',0);
d(cellfun(@isnan,d)) = [];
d = reshape(cell2mat(d),12,[]); % 12 - is values number

But still does not work. Traceback:

Error using readtable (line 143)
Reading failed at line 2. All lines of a text file must have the same number of delimiters. Line 2 has 4
delimiters, while preceding lines have 1.

SAMPLE FILE

PrintScreen

Are there same number of values under every step?

Sardar Usama
– Sardar Usama

2018-03-15 13:30:51 +00:00
Commented Mar 15, 2018 at 13:30 — Sardar Usama
– Sardar Usama, Commented Mar 15, 2018 at 13:30
Yes, there are the same number of values

John
– John

2018-03-15 13:32:16 +00:00
Commented Mar 15, 2018 at 13:32 — John
– John, Commented Mar 15, 2018 at 13:32

Tasos Papastylianou · Accepted Answer · 2018-03-15 20:18:33Z

1

Assuming data has STRICT format, i.e.:
- a line is either a "Step line" or a number
- a "Step line" is necessarily of the format "Step N" where N is an integer
- as many numbers per step can appear

Then here's a solution. Feel free to study it and adapt to your needs.

function Out = readData (In)
  C = strsplit (fileread (In));
  Out = cell(1,1); AtStepcount = false; CurrIndex = 0;

  for I = 1 : length (C)
    if strcmp (C{I}, 'Step'); AtStepcount = true; continue; end
    if AtStepcount
      CurrIndex = str2double(C{I}); Out{CurrIndex} = []; AtStepcount = false; 
      continue
    end
    Out{CurrIndex} = [Out{CurrIndex}; str2double(C{I})];
  end
end

Usage:

V = readData ('myDataFile');

Note: this returns a single cell array, with the step numbers used as indices for each cell element created. This is how you should be doing it anyway; it's generally a bad idea to have variables named "V1", "V2" etc, since you can't iterate using this. With the above solution, your arrays are stored as V{1}, V{2}, etc, and V itself can be used in a for loop.

edited Mar 15, 2018 at 20:18

answered Mar 15, 2018 at 14:33

Tasos Papastylianou

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6 Comments

John Over a year ago

Thank you! On rather small files it is working correct, but if file is huge (aroung 1000 steps) program crushes with "Cell contents indices must be greater than 0" pointing to line Out{CurrIndex} = [Out{CurrIndex}; str2num(C{I})];

Sardar Usama Over a year ago

@Tasos str2num uses eval. You may want to use str2double instead. Double quotes require >= R2017a. The OP is using R2016a. You may want to use single quotes instead.

John Over a year ago

Please, no offense. Just my computational work is stuck here because I can't go further without visualization ..

Tasos Papastylianou Over a year ago

Thanks @SardarUsama, I did not know this. I also didn't even spot I was using double quotes ... dangers of getting used to octave too much, heheh.

Tasos Papastylianou Over a year ago

@John the error tells me that your file probably deviates from the STRICT structure I pointed out. Perhaps there's some sort of inconsistency in the data file that fails? Feel free to share the offending datafile online somewhere for us to test.

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