How can I get only damping and frequency column?

My aim is to extract only numeric values in Damping and Frequency column only. The file, from which I am trying to extract data is very large and contains special character, numbers, text and empty lines. Can anyone please suggest me an efficient way to extract the required data?

I hope the images below gives you a better understanding of the data file. Thanks in advance!!

[Mathieu NOE]

hello

can you zip the file and try to share it (maybe with Google drive or alike)

[Milind Amga]

Here you go :text_file (file has been unlinked later)

You can use notepad to open this file.

Answer 1

[Karim]

Hi,

One approach is to read the whole file, seek some specific line, from that line read the data with a delimiter.

See below for the code, note that i changed the extention to .txt in order to run the demo on the site. It will work fine if you chage the fileID to 'flutter_2d_rh_wing_base.f06'

Best regards

fileID = fopen('flutter_2d_rh_wing_base.f06.txt');
% read the whole file, interpret each line as a string
MyText = textscan(fileID, '%s%[^\n\r]', 'Delimiter', '', 'WhiteSpace', '',  'ReturnOnError', false);
% convert the cell array into a string array, for easier indexing
MyText = string(strtrim(MyText{1}));

% use some logic to find the usefull data blocks
% first the start locations
StartLineIdx = contains(MyText, "KFREQ            1./KFREQ         VELOCITY            DAMPING         FREQUENCY            COMPLEX   EIGENVALUE");
StartLineIdx = find(StartLineIdx) + 1;

% now find the stop locations of each data block
StopLineIdx = contains(MyText, "1    MSC.NASTRAN JOB CREATED ON");
StopLineIdx = find(StopLineIdx) - 1;

% remove some indices that occur before the first start index
StopLineIdx(StopLineIdx<StartLineIdx(1)) = [];

% convert the locations into a single logical array
GetMe = false(size(MyText,1),1);
for i = 1:numel(StartLineIdx)
    GetMe(StartLineIdx(i):StopLineIdx(i)) = true;
end

% extract the usefull strings from the data
MyData = MyText(GetMe);
% exchange double spaces into a single space
MyData = regexprep(MyData, '\s+', ' ');
% use the spaces to split each string
MyData = split(MyData,' ');
% convert the strings into a numeric array
MyData = str2double(MyData);

% extract the columns of intrest
MyDamp = MyData(:,4);
MyFreq = MyData(:,5);

[Milind Amga]

Thank You very much !! I really appreciate your help. It works just like I wanted it to.

[Milind Amga]

If possible, could you please explain me the code? I understood most of it but I still have few doubts like in textscan line, two lines just before the loop and loop as well.

[Karim]

i've added some comments, does this help?

[Milind Amga]

Yes, thanks so much.

[Milind Amga]

@KASR Could you please remove the txt file that you have attached in your previous response.

[Karim]

yes sure, i only added it so that the demo code would work.