how to obtain the number of lines starting with a given string from an external text file and save the numeric value of variables of those lines

Hello,

I have an external text file. A part of the text file (example) is shown below:

/AA
/BB
/CC
DRL=1
DRL=2
DRL=4
/XX
/YY
/ZZ

How can I :

-Obtain the number of lines starting with "DRL" and save it to the variable pnumber. In this case pnumber=3

-save the value of those variables in the vector A, in my example A =[1;2;4]

I thank you in advance for any help,

Best regards,

Hugo

Answer 1

[Sudheer Bhimireddy]

Another approach:

data      = readtable('test.txt');    % test.txt contains the given text
drl_count = sum(strcmp(data.Var1,'DRL'));
drl_value = data.Var2(strcmp(data.Var1,'DRL'));


>> drl_count =

     3

drl_value =

     1
     2
     4

[Hugo]

Hello,

Thank you for your reply. Now I am getting this error:

Unrecognized variable name 'Var1'.

[Sudheer Bhimireddy]

Your actual text file might have column headers. Once you load the data by readtable, open the 'data' variable from your workspace and look if header information is present. In case of missing headers, MATLAB fills the columns by Var1, Var2, ...etc. I just copied the text you pasted in your question and saved it in a text file, so I don't have any headers.

[Hugo]

Hello again!!

Thank you!! Now it works. However, I tried to do minor changes to the code, such as changing the lines

DRL=1

DRL=2

DRL=4

to

DRL1=1

DRL2=2

DRL3=4

And now it does not work. Could you please suggest changes to the code, in order to be able to identify DRL1,2,3...n as starting in 'DRL'??

Thank you for your help.

[Sudheer Bhimireddy]

strcmp(data.Var1,'DRL')

The above line compares the complete field, if you want to comapre against any DRL*, and if that DRL position doesn't change, try this:

drl_count = 0;
drl_value = [];
j = 1;
for i =1:size(data,1)
    flag = strcmp(data.Var1{i}(1:3),'DRL');
    drl_count = drl_count + double(flag);
    if flag
        drl_value(j,1) = data.Var2(i);
        j = j+1;
    end
    
end

[Hugo]

Nice!!! Thank you! It works. But now, I have other problems.

-How can read only the first 10 lines of the text file?

-But first I think I have to convert the original file, in .lgw, to .txt, unless other function than readtable is used.

Thank you once again.

[Sudheer Bhimireddy]

I would say first, try fopen with the .lgw and if it didn't work then convert to txt file.

Try this:

file_ID = fopen('data2.txt','rt'); % Opens file in text mode

% Number of lines to read
nLine_limit = 8; 

% Pre-allocate
data{nLine_limit,1} = 0;

nLine = 1;
% Read first few lines based on nLine_limit
while nLine <= nLine_limit
    data{nLine,1} = fgetl(file_ID); % Read the entire line
    nLine = nLine + 1;
end

fclose(file_ID);

% Filter out the lines with DRL in them and get their indices
drl_Line_Mask = ~cellfun(@isempty, regexp(data,'DRL','match'));

% Seperate all DRL lines
drl_data  = data(drl_Line_Mask);

% Split the cells based on '='
drl_split = regexp(drl_data,'=','split');

% Count number of lines with DRL 
drl_count = numel(drl_split);

% Pre-allocate
drl_value(drl_count,1) = nan;

for i=1:size(drl_split)
    drl_value(i,:)  = str2double(drl_split{i,1}{1,2});
end

[Hugo]

It works perfectly!! Thank you very much!!!

Answer 2

[Ameer Hamza]

Try this

f = fileread('data.txt');
lines = textscan(f, '%s');
lines = lines{1};

idx = cellfun(@(x) x(1)=='/', lines);
lines(idx) = [];

pnumber = numel(lines);
A = cellfun(@(x) sscanf(x, 'DRL=%d'), lines);

data.txt is attached.

[Hugo]

Hello,

Thanks for your reply.

I am getting an error with your approach:

Error using textscan

First input can not be empty. Expected a non-empty character vector or a valid file-id.

Error in calc_test (line 2)

lines = textscan(f,'%s');

[Ameer Hamza]

Have you placed the file data.txt in that folder? data.txt should contain the text in the question.