How to import data from multiple files into MATLAB?

I have multiple text files that I need to import into MATLAB so that I can analyze the data. Here is what I have so far:

 %%import data
x = importdata('1.txt'); %creates x.data and x.textdata
z1 = x.data(:,5); %grabs column 5 from x.data
z2 = x.data(:,6); %grabs column 6 from x.data
%%obtains value closest to 0 in column 'z2'
numb=0;
[~, imin] = min(abs(z2 - numb));
z2(imin)
plot(z1,z2)

How can I import multiple files to run the same operation on every text file? I've tried load(), however, it doesn't seem to work.

Answer 1

[Walter Roberson]

http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

[Asher Zaidi]

That seems to work. It gives me a struct array.

textfiles = dir('*.txt')
for file = textfiles'

    fprintf(1,'Doing something with %s\n',file.name)
end

Result:

2×1 struct array with fields:
  name
  folder
  date
  bytes
  isdir
  datenum
Doing something with 1.txt
Doing something with 2.txt

Then if I use "textfiles.name" it shows me the name of the text files, but how do I access them?

textfiles.name
ans =

    '1.txt'
ans =

    '2.txt'

[Walter Roberson]

{textfiles.name} would be a cell array of the names.

[Asher Zaidi]

How would I go about accessing the data within those files?

[Walter Roberson]

textfiles = dir('*.txt');
filenames = {textfiles.name};
numfiles = length(filenames);

cmap = jet(numfiles);
L = gobjects(numfiles, 1);
alldata = cell(numfiles, 1);

for K = 1 : numfiles
  thisfile = filenames{K};
  thiscolor = cmap(K,:);
  [~, thisbase, ~] = fileparts(thisfile);
  x = importdata( thisfile );
  alldata{K} = x;
  z1 = x.data(:,5); %grabs column 5 from x.data
  z2 = x.data(:,6); %grabs column 6 from x.data
  %%obtains value closest to 0 in column 'z2'
  numb=0;
  [~, imin] = min(abs(z2 - numb));

    L(K) = plot(z1, z2, 'LineColor', thiscolor, 'DisplayName', thisbase);
    hold on
    plot( z1(imin), z2(imin), '*', 'LineColor', thiscolor);
  end
  hold off

legend(L);

[Asher Zaidi]

Very helpful! Thank you!

[hanadi abbas]

I'm used the following codes for loading files , but how can find length of files

for i=1:3

dd1(i)=load(['D:/train/tttt' num2str(i) '.mat'])

end

[Walter Roberson]

Are you asking what the file size is for each .mat file? That can be found by looking at the 'bytes' field returned by dir()

Are you asking how many rows there are in the data you loaded? If so then you would use something like,

for i = 1 : 3
    lens(i) = structfun(@(M) size(M,1), dd1(i), 'uniform', 0);
end

The output, lens would be a non-scalar structure each of which had one field for each variable name in the .mat file, with the content of the field being the number of rows that was stored in that variable in that .mat file. (With the given information, I cannot assume that there is only one variable in each file. I can, though, assume that the files each have the same variable name in the same order, as otherwise the assignment to dd1(i) would fail in your code.)