dlmwrite a matrix into an existing csv file

Dear All,

I do have a a csv file which is basically a 5*6 matrix like the following one:

test.cvs = [1 2 3 4 5 6 
            2 3 4 5 6 7     
            3 4 5 6 7 8 
            4 5 6 7 8 9 
            5 6 7 8 8 8]

Then, I want to dlmwrite the matrix q and at the same time append the data that had been already existed in the csv file. However, I do not want to add matrix q as the 7th row! I like to dlmwrite matrix q in the following way:

q = [11 12 12 12 13]

 test.csv =  [1 2 3 4 5 6 11 12 12 12 13 
              2 3 4 5 6 7 0  0  0  0  0
              3 4 5 6 7 8 0  0  0  0  0 
              4 5 6 7 8 9 0  0  0  0  0 
              5 6 7 8 8 8 0  0  0  0  0 ]

I know that we can use the below command to append by column but I wonder if there is way to append in the way I want it?

   dlmwrite('test.csv', q, 'delimiter', ',', 'precision', 9 ,'-append')

Thanks.

Answer 1

[Walter Roberson]

Try

dlmwrite('test.csv', q, ',', 1, 7, 'precision', 9)

You might have to fill out q with rows of 0's.

[Homayoon]

thanks but was there any reason that you removed 'delimiter' ?

[Homayoon]

And also the command does not work! Gave me an error.

[Walter Roberson]

'delimiter' is positional when you use that form of row and column offset.

    dlmwrite('FILENAME',M,'DLM',R,C) writes matrix M starting at
    offset row R, and offset column C in the file.  R and C are zero-based,
    so that R=C=0 specifies the first value in the file.

However it turns out that if you do not use -append then it still erases the file, and that if you do use -append then it goes to the end of the file and writes after that, not appending in-place.

The solution would appear to be to use xlswrite() if you are using an MS Windows system with Excel installed. If you are using Linux or OS-X or do not have Excel installed, then xlswrite() operates in Basic mode that ignores the position offsets and so would not work for this situation.

Universal work around: read the existing data, put the new content onto the side of that, write out the augmented data.

data = csvread('test.cvs');
data(1,end+1:end+length(q)) = q;
dlmwrite('test.cvs', data, 'Delimiter', ',', 'Precision', 9);