MATLAB Answers

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

39 views (last 30 days)
Hugo
Hugo on 28 Sep 2020 at 15:45
Commented: Hugo on 29 Sep 2020 at 14:54
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

  0 Comments

Sign in to comment.

Accepted Answer

Sudheer Bhimireddy
Sudheer Bhimireddy on 28 Sep 2020 at 15:58
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

  7 Comments

Show 4 older comments
Hugo
Hugo on 29 Sep 2020 at 9:22
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
Sudheer Bhimireddy on 29 Sep 2020 at 13:33
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

Sign in to comment.

More Answers (1)

Ameer Hamza
Ameer Hamza on 28 Sep 2020 at 15:50
Edited: Ameer Hamza on 28 Sep 2020 at 15:50
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.

  2 Comments

Hugo
Hugo on 28 Sep 2020 at 16:49
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');

Sign in to comment.

Tags

Products


Release

R2018b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by