Plotting several .txt files

I want to read several .txt files and plot the 4th and 5th columns of each of them in just one grap. I tried adapting the code from Here but the graph appears blank. IF it would be possible, I would also like to put and identification on each 2D line. Here is what I got so far,

myFolder = 'Users\adminstrator\Desktop\Curves';
filePattern = fullfile(myFolder, '*.txt');
theFiles = dir(filePattern);
for k = 1 : length(theFiles)
    baseFileName = theFiles(k).name;
    fullFileName = fullfile(theFiles(k).folder, baseFileName);
    fprintf(1, 'Now reading %s\n', fullFileName);
    plot(fullFileName(:,4),fullFileName(:,5));
    hold on
end
hold off

Answer 1

[dpb]

...
fullFileName = fullfile(theFiles(k).folder, baseFileName);
fprintf(1, 'Now reading %s\n', fullFileName);
plot(fullFileName(:,4),fullFileName(:,5));
...    

You created a fully-qualified file name, but you never used it to read the file.

Your plot() command uses the filenames as variables for x,y but those are the names of the files, the name doesn't contain the data in the file; you have to read it some way.

The code link you used as a pattern was looking at .png files so it used

...
% such as reading it in as an image array with imread()
imageArray = imread(fullFileName);
imshow(imageArray);  % Display image.
...

to read and display the image in the file. Your simple text file format with no header line will be easy with

...    
fullFileName = fullfile(theFiles(k).folder, baseFileName);
disp(['Now reading ', fullFileName])
data=readmatrix(fullFileName);
plot(data(:,4),data(:,5));
...

As written, each loop will replace the preceding line with the next; you're missing a key element to plot all on one graph--"hold". Read documenation for it to get the bigger picture...

You could also streamline the sample code a little; it was written to make every step obvious which isn't all bad...

myFolder = 'Users\adminstrator\Desktop\Curves';
d=dir(fullfile(myFolder, '*.txt'));
figure, hold on
for k = 1:numel(d)
  data=readmatrix(fullfile(d(k).folder,d(k).name);
  plot(data(:,4),data(:,5));
end

[Feliciano Döring]

Thanks! I understand it now, but I still get a blank graph after running the code

[dpb]

Did you check d returned a non-empty result? IOW, that there were/are actually files where you're looking?

Use the debugger and step through to see where the issue lies; the code looks as though it would be fine.

[Feliciano Döring]

Yes, apparently it is returning a 0x1 struct, but I have the code in the same folder as the files, and the path is correct.

[dpb]

Typo? There's a reason but we can't see your terminal from here...what does

pwd

return?

Don't need a drive letter by any chance?

If the code and files are in same directory, then you should be able to just use

d=dir('*.txt');

Does that return expected result at command line?

[Feliciano Döring]

Yes, I forgot the drive, thanks! And substituting

d=dir(fullfile(myFolder, '*.txt'));

for

d=dir('*.txt');

yielded good results, the only problem is my version of Matlab is 2015a, and as I researched the folder field was added only in 2016a, so that is why it is not working. But thanks!

Edit:I substituted the

data=readmatrix(fullfile(d(k).folder,d(k).name);

with

data=dlmread(myFolder,d(k).name);

And it worked.