Copy and paste data in the same CSV file using matlab

Hello, I have a CSV file with 720 rows and 2 columns. First column of the file has to be extrapolated to 1420 rows with some function and second column has to be extrapolated to 1420 rows by copying/repeating the same data as in first 720 rows (original data present in second column). I am Successful in extrapolating the first column but getting stuck in the second column. Can anybody help me? Example:

Original file

0.0   0.82
2.1   0.72
4.2   0.68 
6.3   0.15

Modified file

0.0   0.82
2.1   0.72
4.2   0.68 
6.3   0.15
8.4   0.82
10.5  0.72
12.6  0.68
14.7  0.15

[Stephen23]

It is much easier for us if you actually upload a sample file for us to use. This is because peoples descriptions of files, the formatting of HTML text and trying to copy it makes this process very error-prone.

You can upload using the paperclip button, and then pressing both the Choose file and Attach file buttons.

It also helps uf if you format any code correctly using the {} Code button that you will find just above the textbox.

Answer 1

[Stephen23]

Method One Hard-coded replication of rows (twice in this example):

>> X = [0.0,0.82; 2.1,0.72; 4.2,0.68; 6.3,0.15];
>> D = mean(diff(X(:,1)));
>> Y(:,2) = [X(:,2);X(:,2)];
>> Y(:,1) = [X(:,1);X(:,1)+X(end,1)+D]
Y =

           0    0.8200
      2.1000    0.7200
      4.2000    0.6800
      6.3000    0.1500
      8.4000    0.8200
     10.5000    0.7200
     12.6000    0.6800
     14.7000    0.1500

Method Two Number of rows replicated by a constant (thrice in this example):

>> N = 3;
>> Z(:,2) = repmat(X(:,2),N,1);
>> Z(:,1) = linspace(0,D*(N*size(X,1)-1),size(Z,1))
Z =
       0    0.8200
  2.1000    0.7200
  4.2000    0.6800
  6.3000    0.1500
  8.4000    0.8200
 10.5000    0.7200
 12.6000    0.6800
 14.7000    0.1500
 16.8000    0.8200
 18.9000    0.7200
 21.0000    0.6800
 23.1000    0.1500

[GS]

It works fine, thank you very much for your help