Replace comma with dot after fopen

Hello everyone,

I am having some problems with Matlab.

I import a txt file with fopen and, after imported, I want to convert the commas in the file with dots but I do not know how to do. I have searched between the answers in the Matlab Central but I have found nothing.

Thank you for the help.

[KSSV]

Read about strrep.

[Stephen23]

"I have searched between the answers in the Matlab Central but I have found nothing"

Here are 339 results, many of which are related to file importing:

https://www.mathworks.com/matlabcentral/answers/?term=decimal+comma

[Daniele Sonaglioni]

@KSSV Thanks but it does not help me because it must be used before fopen (as far as I have seen).

I attach a part of my code to let you know what I am working on:

fidi = fopen('myfile.txt','rt');
k1 = 1;
while ~feof(fidi)
    readline = fgetl(fidi);
    
    if strcmp(readline,'Results:')
        C = textscan(fidi, '%f%f%f%f %*f%*f%*f%*f%*f%*f', 'HeaderLines',9, 'CollectOutput',1);
    else
        C = textscan(fidi, '%f%f%f%f %*f%*f%*f%*f%*f%*f', 'HeaderLines',0, 'CollectOutput',1);
    end
    M = cell2mat(C);
    fprintf(1,'\tSection %2d: (%4d x %d)\n', k1, size(M));
    if isempty(M)                                           % Empty Matrix Indicates End-Of-File
        fprintf(1,'Reading finished, %d Sections\n',k1-1);
        break
    end
    D{k1,:} = M;
    fseek(fidi, 0, 0);
    k1 = k1 + 1;
end
fclose(fidi);

[Daniele Sonaglioni]

@Stephen I am aware that there are results on the Matlab Central (I have also checked them) but I have not found anything useful.

I know that before asking question one has to check on the central.

Answer 1

[Star Strider]

For MATLAB versions R2019a and later, the readmatrix function permits definition of the 'DecimalSeparator' (see the Text Files Only documentation section, since ther is no direct link to it) as a name-value pair argument.

.

[Daniele Sonaglioni]

Your idea is quite good but using readmatrix will result in a great change in the code and this is something I want to avoid. I have attached the code in my previous answer, maybe you remeber it: can you suggest something about that code?

[Star Strider]

I don’t remember it, however that looks like my code.

One possibility would be to read the variables in a strings rather than numeric, then use strrep on the strings, and then read the entire line using textscan.

Another option would be to read the entire file as text using the fileread funciton, then do the conversion and use textscan, since it can take character vectors as input.

Attaching the file would help.

.

[Daniele Sonaglioni]

This the kind of file I want to convert.

[Star Strider]

Since you stated that using readmatrix (or readtable) would disrupt your existing code, an alternative would be textscan.

The online Run feature would not let me do all this here, so I did it offline —

fidi = fopen('trial_file.txt','rt');
C = textscan(fidi, '%f%s%s%s', 'HeaderLines',10, 'CollectOutput',1, 'EndOfLine','\r\n');
fclose(fidi);
M = [C{1} str2double(strrep(C{2},',','.'))];

Check = M(1:5,:)

Check =

            0            0      -19.773    -0.009783
            1        0.001      -19.733    -0.015429
            2        0.002      -19.655    -0.038148
            3        0.003      -19.564    -0.081012
            4        0.004      -19.462     -0.13152

That imports the file and coinverts it correctly so it can be used in computations.

.

Answer 2

[Stephen23]

fnm = 'trial_file.txt';
opt = detectImportOptions(fnm, 'VariableNamesLine',9, 'VariableUnitsLine',10, 'DecimalSeparator',',', 'ExtraColumnsRule','ignore');
opt.DataLines = [11,Inf];
tbl = readtable(fnm, opt)

tbl = 69227×4 table
    Index      t        Ts         Value  
    _____    _____    _______    _________

      0          0    -19.773    -0.009783
      1      0.001    -19.733    -0.015429
      2      0.002    -19.655    -0.038148
      3      0.003    -19.564    -0.081012
      4      0.004    -19.462     -0.13152
      5      0.005     -19.36     -0.17076
      6      0.006    -19.262     -0.19742
      7      0.007    -19.161     -0.21605
      8      0.008    -19.061     -0.22971
      9      0.009     -18.96     -0.24071
     10       0.01    -18.861     -0.24984
     11      0.011     -18.76     -0.25674
     12      0.012    -18.661     -0.26249
     13      0.013     -18.56     -0.26758
     14      0.014    -18.461     -0.27248
     15      0.015     -18.36     -0.27657