Trouble getting multiple text file loop to work

Hi, I have spent about two weeks getting upto this point and cant seem to crack it. I get an error message of ''Undefined function or variable 'II'.' and variables I l S also as undefined so the problem seems to be with I l s and not II as such.

I have about 20 or so text files that I need to perform simple interpolation and integration. the text files have one header, and three columns of numbers which are tab delimited. I am pretty sure the problem is textscan or my use of it because previously I had:

[I,l,s]=textread('filename','%f %f %f','headerlines',1);

and this gave me the column outputs nicely but I could not get a loop to work with textread to go through all files in a directory.

if true
%
path='Z:\Year 3\FEA assignment\Matlab';
D=dir(fullfile('path', '*.txt'));
for k=1:numel(D)
  fid=fopen(fullfile(path, D(k).name), 'r');
  data=textscan(fid,'%f %f %f','headerlines',1)
  data{1}=I;
  data{2}=l;
  data{3}=s;
  fclose(fid);
  for i=1:l(end)
      if  s(i)<0
          na=l(i);
          i;
          % linear interpolate distance to zero stress
          p1=[l(i-1) s(i-1)];
          p2=[l(i) s(i)];
          % Equation of line - y=gradx+c
          grad=(p2(2)-p1(2))/(p2(1)-p1(1));
          c=p1(2)-grad*(p1(1));
          % Set y=0 to get neutral axis position
          x=-c/grad ;
          fprintf('Distnce to Neutral axis is %.2f mm \n', x)
          break    
      end
      % Remove all -ve stress from vectors
      for j=1:i
          II(j)=I(j);
          ll(j)=l(j);
          ss(j)=s(j);
      end
  end   
end

 % Combine All positive with interpolated point
II=[II II(end)+1];
ll=[ll x];
ss=[ss 0];

 % Convert to standard units
L=ll/(1e3);    % In m
S=ss*(1e6);    % In Pa
A=trapz(L,S);  % Integrate Points V by spacing of L

 % Find average stress (height)
Snom=(A)/L(end);  % Use only distance to neutral axis
SCF=S/Snom;
m=max(SCF);
fprintf('Nominal Stress= %.3g(Pa)\nKt= %.2f \n',Snom, m)code

Answer 1

[Y.Nadiree]

Ok, managed to loop through all files by changing the start bit to

all_files=dir('*.txt');
  for k=1:1:length(all_files);
     filename=all_files(k).name;
     fid=fopen(filename,'r');
     C=textscan(fid,'%f %f %f','Headerlines',1);
     fclose(fid);

       I=C{1};  % Index
       l=C{2};  % Length(mm)
       s=C{3};  % Stress(MPa)
    end
rest of code same as before

However one little problem remains which is for some reason it reuses some variables from previous loops because if I do the operation on a single file the results is different than when that same file is done after others in a loop. I tried putting clear before the final end command but seems to break the loop giving error ??? Undefined variable "all_files" or class "all_files" after the first file.

I know it is reusing data from previous files also because the plot of the graphs look odd and the same as when I manually ran some files without clearing variables so that is my problem for now.

Answer 2

[Y.Nadiree]

Solved the problem, before the final end just added

clearvars -except all_files

Hope it helps someone else.