How should I write a code that can realize if a text file is updated and the code updates my plot too?

I have a log file which is keep updating a message (text file attached). This message can somehow be plotted and I have done that (see below) but I don't know how to update my plot when the txt file is updated with a new line?

logfile = uigetfile
opt = detectImportOptions(logfile,'FileType','text','Delimiter',','); % setting import options
opt.VariableNames = {'LogType','RealTimeStamp','DataSet','ParticleTimeStamp','ForcedParticleFlag','TriggerIntensity','Channel2','Channel3','Channel4','Channel5','Channel6','Channel7','Channel8','Channel9','Channel10','Channel11','Channel12','Channel13','Channel14','Channel15','Channel16','Channel17','Channel18','Channel19','Channel20','Channel21','Channel22','Channel23','Channel24','Channel25','Channel26','Channel27','Channel28','Channel29','Channel30','Channel31','Channel32'};
opt.ExtraColumnsRule ='ignore';      % remove extra column
ImportLog = readtable(logfile,opt);   % import log file
ImportLog=ImportLog(~any(ismissing(ImportLog),2),:); % import only scattering data and remove other data
ChannelToAngle_T = PHIPS_ChannelToAngle(ImportLog);      % channel to angle table
ForcedTrigger = ChannelToAngle_T.ForcedParticleFlag; % forced trigger out of table
idx0 = find(ForcedTrigger == 0);                      % index of those lines that has forced trigger or not
idx1 = find(ForcedTrigger == 1);  

for i= 1:numel(idx0)
  
    Angle = 18:8:170;                            % Angles
    ASF = table2array(ChannelToAngle_T(idx0(end), end-19:end)); % Angular Scattering Function
    semilogy(Angle, ASF, 's-','MarkerFaceColor', 'w', 'LineWidth', 2, 'MarkerSize', 10) % plot
    hold on
    %semilogy(angle, ASF_2, 's--','MarkerFaceColor', 'w', 'LineWidth', 2, 'MarkerSize', 10)
    %semilogy(angle, ASF_3, 's--','MarkerFaceColor', 'w', 'LineWidth', 2, 'MarkerSize', 10)
    hold off
    grid on
    xlabel ('Scattering Angle')
    ylabel ('Scattering Intensity [cts]')
    ylim([0, 5000])
    ax = gca;
    ax.YAxis(1).Color = 'k'; % change color of LHS y-axis to black
    % ax.YAxis(2).Color = 'k'; % change color of RHS y-axis to black
    ax.FontSize = 14; 
    ax.FontWeight = 'bold';
    legend('Location', 'southeast')
%     

end

Answer 1

[Image Analyst]

You could periodically check the date of the file with dir() (in a for loop or with a timer) and if the file date changed from the last time you checked it, update your plot.

[Sepehr Ariaei]

Thank you @Image Analyst. Could you please show it to me with an example?

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/99277-how-do-i-programmatically-detect-a-change-in-a-directory

[Sepehr Ariaei]

@Walter Roberson

Thank you. I decided to use the dir() and

size0 = FileInfo.bytes

to compare my files. and how should I put the plot in the loop that it updates. This part of the logic I cannot understand. I want it to just rewrite the same plot over and over again. Something like below:

if size1>=size0

while something

????

end

end

[Walter Roberson]

If you are updating everything, then just cla() and redraw everything.

If you want to just update one particular line without disturbing anything else, then I recommend you look at animatedline()

[Walter Roberson]

if size1>=size0

You have the problem that the fact that a file has increased in size does not mean that the new last line in the file is complete. Unless the program is using line buffering (flushing after every line), then it might be in the middle of writing something out at the time you check.

At the moment I cannot tell whether you are using Windows or Mac or Linux. If you are using Windows then there is the additional risk that the file might be locked .

[Sepehr Ariaei]

@Walter Roberson

The lines are sent via a Windows console as a UDP message which I think (not sure) would be a packet of data but I am not completely sure how it's stored as a log file. I need to ask our software engineer. I am actually using this in a Matlab App so that is why I am a little confused how to put this plot in a while loop. I need to use semilogy to demonstrate this data. I will use the timer instead but can you please explain this while loop I wanna put in matlab app?

[Walter Roberson]

how_long_to_wait = 5;
[logfile, logdir] = uigetfile;
if ~ischar(logfile); return; end     %user cancel
logfile = fullfile(logdir, logfile);

opt = detectImportOptions(logfile,'FileType','text','Delimiter',','); % setting import options
opt.VariableNames = {'LogType','RealTimeStamp','DataSet','ParticleTimeStamp','ForcedParticleFlag','TriggerIntensity','Channel2','Channel3','Channel4','Channel5','Channel6','Channel7','Channel8','Channel9','Channel10','Channel11','Channel12','Channel13','Channel14','Channel15','Channel16','Channel17','Channel18','Channel19','Channel20','Channel21','Channel22','Channel23','Channel24','Channel25','Channel26','Channel27','Channel28','Channel29','Channel30','Channel31','Channel32'};
opt.ExtraColumnsRule ='ignore';      % remove extra column

ax = app.axes1;
cla(ax)
ax.YScale = 'log';
h = plot(nan, nan, 's-','MarkerFaceColor', 'w', 'LineWidth', 2, 'MarkerSize', 10);

oldsize = -inf;
while true
   FileInfo = dir(logfile);
   if FileInfo.bytes > oldsize
      oldsize = FileInfo.bytes;
      ImportLog = readtable(logfile,opt);   % import log file
      do some stuff
      h.XData = Angles; h.YData = ASF;
      drawnow();
   else
       pause(how_long_to_wait)
   end
end

[Image Analyst]

Does it always increase in size? If not then you could replace

if FileInfo.bytes > oldsize

with

if FileInfo.bytes ~= oldsize

Answer 2

[Sepehr Ariaei]

It always increase in size.

Thank you very much for your helps. It worked. @Image Analyst @Walter Roberson