adding data to a text file

Asked by lowcalorie on 15 Mar 2012

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i have a file called hello.txt using wordpad which contains the matrix

2 7 3

2 6 9

now i have a vector v = [1 2 3] and i want to add this vector to the hello.txt file so when i open the hello.txt file i should have

2 7 3

2 6 9

1 2 3

how can i do this

1 Comment

Walter Roberson on 15 Mar 2012

Duplicate is at http://www.mathworks.com/matlabcentral/answers/32377-appending-a-file

2 Answers

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Answer by Wayne King on 15 Mar 2012

Accepted Answer

You can use:

dlmwrite('FILENAME',M,'-append')

For example:

x = [2 7 3; 2 6 9];
dlmwrite('test.dat',x);
y = [1 2 3];
dlmwrite('test.dat',y,'-append');

4 Comments

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Wayne King on 15 Mar 2012

and you are using '-append'??? Just copy and paste my example, it works.

lowcalorie on 15 Mar 2012

if i already have a file what fopen should i be using

Walter Roberson on 15 Mar 2012

Wayne's code is designed for the case where the file is _not_ open.

The code that opens the file is shown in your duplicate question, referenced in the above comments.

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Answer by Geoff on 15 Mar 2012

I remember answering an almost identical question from you the other day. It used the fopen() with the open-mode 'w' to overwrite.

To append, use the open-mode 'a'.

2 Comments

lowcalorie on 15 Mar 2012

thats what im doing but it keeps overwriting there muct be something wrong with other parts of my script then

thanks

Walter Roberson on 15 Mar 2012

"lowcalorie" is using WordPad to examine the file. "at" is needed instead of just "a", as WordPad is an old editor that only understands lines if they end in the combination CARRIAGE-RETURN LINEFEED which you do not get if you use only "a" permissions when you are using MS Windows.

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adding data to a text file

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