adding data to a text file

Question

lowcalorie 2012-3-15

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https://ww2.mathworks.cn/matlabcentral/answers/32407-adding-data-to-a-text-file

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

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Walter Roberson 2012-3-15

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

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Answer 1

Wayne King 2012-3-15

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https://ww2.mathworks.cn/matlabcentral/answers/32407-adding-data-to-a-text-file#answer_40956

在 MATLAB Online 中打开

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');

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lowcalorie 2012-3-15

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

Walter Roberson 2012-3-15

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 2

Geoff 2012-3-15

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https://ww2.mathworks.cn/matlabcentral/answers/32407-adding-data-to-a-text-file#answer_40962

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'.

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lowcalorie 2012-3-15

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

thanks

Walter Roberson 2012-3-15

"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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