fileDatastore of files with different extensions

Hi all,

I have attached a live script file.

I am trying to import a number of text files that have an *.out file extension, into a datastore function. I have attached a few of this files in a zipped file.

I am trying to extract the numerical data under the "'COS(NT)" and "SIN(NT)" headings in each file.

I am using the datastore function as I thought this maybe better than trying to loop through the files after creating variables for the file. I am new to programming and Matlab, hence my struggles.

Any assistance and/or suggestions would be much appreciated.

Regards,

Gary

Answer 1

[Nimit Dhulekar]

Hi Gary,

I looked at the attached files and it appears that you are only interested in data in a handful of lines (4 to be exact) in a significantly large file. If the data happens to appear consistently on the same lines in the file, you could consider creating a fixed width import options object and setting the DataLines property. You can then pass this object to readtable in your custom reader function that you supplied to fileDatastore.

fds = fileDatastore("Out/", "ReadFcn", @myCustomReader, "FileExtensions", ".out");
read(fds)

function R = myCustomReader(filename)
opts = delimitedTextImportOptions("NumVariables", 6, "DataLines", ...
    [70849:70850; 70910:70911], "VariableTypes", ...
    ["char", "char", "double", "double", "double", "double"], ...
    "Delimiter", "  ");
R = readtable(filename, opts);
R.Var1 = []; % Note that the initial space on the data line appears as varaibles and has to be manually removed
R.Var2 = [];
end

However, if your data is not expected to appear on the same line in every file, then you would have to use a more complicated approach. A code pattern similar to the following should work.

function R = myCustomReader(filename)
F = fileread(filename);
Fsplits = split(F, newline);
F_varArray = contains(Fsplits, "COS(NT)");
idx = find(F_varArray == 1);
row1 = Fsplits(idx(1)+2);
row2 = Fsplits(idx(1)+3);
row3 = Fsplits(idx(2)+2);
row4 = Fsplits(idx(2)+3);

splitRow1 = split(row1, "  ");
splitRow1(1:2) = [];
val1 = str2double(splitRow1');

splitRow2 = split(row2, "  ");
splitRow2(1:2) = [];
val2 = str2double(splitRow2');

splitRow3 = split(row3, "  ");
splitRow3(1:2) = [];
val3 = str2double(splitRow3');

splitRow4 = split(row4, "  ");
splitRow4(1:2) = [];
val4 = str2double(splitRow4');

R = table([val1; val2; val3; val4]);
end

Hope this helps.

[GS76]

Thank you so much for your reply in this regard.

The second "myCustomReader" worked great. Is it possible run this routine with multiple files at once?

I am getting the following error when I run the first 2 lines. Please see the screen shot below. Could you perhaps assist? Thank you again.