MATLAB Answers

KOU DU
0

How to skip first three lines in Matlab and read the next line until fixed character appears?

Asked by KOU DU
on 27 Mar 2019
Latest activity Commented on by KOU DU
on 31 Mar 2019
I have a input txt file as shown below:
*Heading
U:/Mesh_Sphere_faible.inp
*Node
1, 0.061725, 0.271605, 0.41523577
2, 0.05795391, 0.39902727, 0.29566634
3, 0.012345, 0.054321, 0.083047155
*Element, type=C3D10, ELSET=PART1
1, 150, 1278, 1280, 1282, 3738, 3742, 3740,
3739, 3741, 3743
2, 62, 700, 702, 704, 2342, 3747, 3745,
3744, 3746, 3748
3, 242, 1863, 1866, 1865, 3749, 3753, 3751,
3750, 3752, 3754
I want to read the data after line of '*Node'. I have tried
A=dlmread('Mesh_Sphere_faible.dat','',4,0)
but always stopped at line:
2, 0.05795391, 0.39902727, 0.29566634
How can I realise it?
And I also want to read until line
*Element, type=C3D10, ELSET=PART1
appears.
What can I do?

  2 Comments

Could you confirm that the lines alternate between 8 comma separated values (with trailing comma on the line) followed by 3 comma separated values?
Or is that just a result of how it was posted, and all of those values are on the same line?
Can you attach a sample file for certainty ?
Yes, of course. It's clearer if I attach a sample file.
When you see data after *Element like
1, 150, 1278, 1280, 1282, 3738, 3742, 3740,
3739, 3741, 3743
It means they are in the same element but not show in the same line.
I need read them in the same line by Matlab.
Thank you for your answer.

Sign in to comment.

3 Answers

Answer by Image Analyst
on 29 Mar 2019
 Accepted Answer

This will do it:
% Open the file.
fullFileName = fullfile(pwd, 'example.txt')
fileID = fopen(fullFileName, 'rt');
% Read the first 3 lines of the file.
textLine = fgetl(fileID); % Read and throw away line 1
textLine = fgetl(fileID); % Read and throw away line 2
textLine = fgetl(fileID); % Read and throw away line 3
data = [];
while ischar(textLine)
% Read the next line.
textLine = fgetl(fileID);
% Print out what line we're operating on.
fprintf('%s\n', textLine);
if ~contains(textLine, 'Element')
numbers = sscanf(textLine, '%f,')
data = [data; numbers'];
else
break;
end
end
% All done reading all lines, so close the file.
fclose(fileID);
% Show in command window.
data

Answer by Niti K
on 27 Mar 2019

you can use the function fgetl. you can open the file in read mode using fopen and set up a while loop with the file id.
sort of a pseudocode
1) open the file using fopen
2) utilizing a loop, use getl which will fetch all the characters in the current line. Each usasge of getl will fetch the next line in your file
3) string split the output from getl using space delimeter
4) use string compare to check whether first worf from string split matches your criteria (*node in this case)
5) you can then read the data you want untill you encounter (*element)
exit out of the loop

Answer by Akira Agata
on 29 Mar 2019

Another possible solution:
% Read the file as a text
fid = fopen('Example.txt','r');
C = textscan(fid,'%s','Delimiter','\n');
C = C{1};
fclose(fid);
% Find row numbers which contains the words 'Node' and 'Element'
row1 = find(contains(C,'Node'));
row2 = find(contains(C,'Element'));
% Extract data rows
C = C(row1+1:row2-1);
% Convert to numeric matrix
D = cellfun(@(x) str2double(strsplit(x,',')),C,'UniformOutput',false);
D = cell2mat(D);

  1 Comment

Sign in to comment.