How to extract continued values from for cycle

Question

Stefano Alberti 2016-2-12

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https://ww2.mathworks.cn/matlabcentral/answers/267813-how-to-extract-continued-values-from-for-cycle

评论： Brattv 2016-2-12

I've a for cycle that processed thousand files, I don't succeed to take for each for cycle the values generated and store it into a table (or cell or matrix..).

Example:

for cycle return: 1 cycle --> t1 and t2

2 cycle --> t3 and t4

.... n cycle --> tn1 and tn2

creata a table (or something like that to store and give accesible the data) with two separates columns like this:

t1 t2

t3 t4

...

tn1 tn2

Thanks in advance

Stefano

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Answer 1

Brattv 2016-2-12

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Hi, I am not sure if t1 and t2 are scalars or vectors/matrices, but is this what you are looking for?

% number of files 
n = 1000;
% Making a empty matrix 
storeValues = []; 
for i=1:n
    % Making random numbers as example
    t1 = rand(1);
    t2 = rand(1);
    % Storing values in matrix 
    storeValues(i,:) = [t1 t2];
end
% Printing vector in command window
storeValues

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Stefano Alberti 2016-2-12

在 MATLAB Online 中打开

Really good idea Vegard, thansks.

I try to put this part of code in my code, but I don't know what do I do wrong but now storeValues repeat the same char for each box.

% Making a empty matrix 
storeValues = []; 
   for k =1:3 %numel(D)
      fid = fopen(fullfile(D(k).name), 'rt');
      filename = D(k).name ;
      a=filename(11:end);
      b=regexp(a,'__','split');
      out1=cellfun(@(x) datestr(datenum(x(1:10),'yyyy_mm_dd'),'yyyy/mm/dd'),b,'un',0);
      out2=cellfun(@(x) datestr(datenum(x(12:end),'HH_MM'),'HH:MM'),b,'un',0);
      out=[out1'  out2'];
      prova = [out{1,1}, ' ', out{1,2}];
      prova2 = [out{2,1}, ' ', out{2,2}];
      format shortg;
      t1 = datevec(prova,'yyyy/mm/dd HH:MM');
      t2 = datevec(prova2,'yyyy/mm/dd HH:MM');
      for i=1:length(D)
      % Making random numbers as example
      t11 = t1;
      t22 = t2;
      % Storing values in matrix 
      storeValues(i,:) = [t1 t2];
  end
  % Printing vector in command window
  storeValues
      e=etime(t2, t1)
      clearvars out1 out2 t1 t2;
      fclose(fid);
  end

Stephen23 2016-2-12

编辑：Stephen23 2016-2-12

Have you read my answer ?

It might resolve a lots of your code problems.

PS: you might also start to learn why it is a bad idea to ask many questions on the same topic: because you cannot keep track of what information people have given you.

Brattv 2016-2-12

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You need to keep track of your variable types. Use a cell to store the date data that datestr returns. You should also remove the for loop inside the loop.

% Making a empty matrix 
  storeValues = cell(1,2); 
     for k =1:3 %numel(D)
        fid = fopen(fullfile(D(k).name), 'rt');
        filename = D(k).name ;
        a=filename(11:end);
        b=regexp(a,'__','split');
        out1=cellfun(@(x) datestr(datenum(x(1:10),'yyyy_mm_dd'),'yyyy/mm/dd'),b,'un',0);
        out2=cellfun(@(x) datestr(datenum(x(12:end),'HH_MM'),'HH:MM'),b,'un',0);
        out=[out1'  out2'];
        prova = [out{1,1}, ' ', out{1,2}];
        prova2 = [out{2,1}, ' ', out{2,2}];
        format shortg;
        t1 = datevec(prova,'yyyy/mm/dd HH:MM');
        t2 = datevec(prova2,'yyyy/mm/dd HH:MM');
        % Storing values in matrix 
        storeValues(i,:) = [cellstr(t1), cellstr(t2)];
    end
    % Printing vector in command window
    storeValues