# How to specify number of decimals in table2word or writematrix

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Gerrit on 23 Aug 2023
Commented: Gerrit on 24 Aug 2023
Is it possible to write a double-valued matrix/array to a Word (or comma-separated text file) table with a specified format, e.g. a fixed-point notation with a specified number of decimals?
By default, writematrix seems to use "longg (15 digits of precision)" (see Guillaume's comment in
).
Function table2word seems to produce a fixed-point notation with 6 decimal digits, for example 0.999763. Four decimals would be enough for me, to limit the table size in the Word document.

Voss on 23 Aug 2023
Edited: Voss on 23 Aug 2023
A random matrix:
M = rand(10,10); % matrix to write to file
fn = 'example.csv'; % file to write to
disp(M); % show the matrix for reference
0.0875 0.0521 0.8735 0.2275 0.9665 0.9244 0.9738 0.6341 0.9535 0.1825 0.2008 0.7956 0.6300 0.8176 0.8290 0.2900 0.0079 0.2002 0.1766 0.2160 0.7700 0.2851 0.8427 0.7191 0.7268 0.6323 0.6483 0.2989 0.0995 0.0482 0.7619 0.5196 0.5693 0.0790 0.9315 0.5310 0.8457 0.5849 0.7667 0.1528 0.1522 0.9690 0.0655 0.5860 0.3579 0.3156 0.7562 0.1719 0.4301 0.7786 0.9014 0.0027 0.1264 0.0835 0.8795 0.8506 0.2957 0.4463 0.7743 0.8732 0.4047 0.1415 0.2763 0.3467 0.2525 0.5155 0.7914 0.7816 0.6304 0.4213 0.0221 0.8341 0.3272 0.3642 0.9500 0.5038 0.8380 0.4023 0.7816 0.0560 0.1109 0.7316 0.5988 0.0174 0.0255 0.8042 0.6785 0.0685 0.8624 0.4913 0.3914 0.6016 0.6013 0.4869 0.4036 0.7793 0.6142 0.4322 0.5552 0.0047
One way to write the file:
fid = fopen(fn,'w');
fprintf(fid,[repmat('%.4f,',1,size(M,2)) '\n'],M.');
fclose(fid);
type(fn); % check the file
0.0875,0.0521,0.8735,0.2275,0.9665,0.9244,0.9738,0.6341,0.9535,0.1825, 0.2008,0.7956,0.6300,0.8176,0.8290,0.2900,0.0079,0.2002,0.1766,0.2160, 0.7700,0.2851,0.8427,0.7191,0.7268,0.6323,0.6483,0.2989,0.0995,0.0482, 0.7619,0.5196,0.5693,0.0790,0.9315,0.5310,0.8457,0.5849,0.7667,0.1528, 0.1522,0.9690,0.0655,0.5860,0.3579,0.3156,0.7562,0.1719,0.4301,0.7786, 0.9014,0.0027,0.1264,0.0835,0.8795,0.8506,0.2957,0.4463,0.7743,0.8732, 0.4047,0.1415,0.2763,0.3467,0.2525,0.5155,0.7914,0.7816,0.6304,0.4213, 0.0221,0.8341,0.3272,0.3642,0.9500,0.5038,0.8380,0.4023,0.7816,0.0560, 0.1109,0.7316,0.5988,0.0174,0.0255,0.8042,0.6785,0.0685,0.8624,0.4913, 0.3914,0.6016,0.6013,0.4869,0.4036,0.7793,0.6142,0.4322,0.5552,0.0047,
Another way:
C = compose('%.4f,',M.');
C(end+1,:) = {newline()};
fid = fopen(fn,'w');
fprintf(fid,'%s',C{:});
fclose(fid);
type(fn); % check the file
0.0875,0.0521,0.8735,0.2275,0.9665,0.9244,0.9738,0.6341,0.9535,0.1825, 0.2008,0.7956,0.6300,0.8176,0.8290,0.2900,0.0079,0.2002,0.1766,0.2160, 0.7700,0.2851,0.8427,0.7191,0.7268,0.6323,0.6483,0.2989,0.0995,0.0482, 0.7619,0.5196,0.5693,0.0790,0.9315,0.5310,0.8457,0.5849,0.7667,0.1528, 0.1522,0.9690,0.0655,0.5860,0.3579,0.3156,0.7562,0.1719,0.4301,0.7786, 0.9014,0.0027,0.1264,0.0835,0.8795,0.8506,0.2957,0.4463,0.7743,0.8732, 0.4047,0.1415,0.2763,0.3467,0.2525,0.5155,0.7914,0.7816,0.6304,0.4213, 0.0221,0.8341,0.3272,0.3642,0.9500,0.5038,0.8380,0.4023,0.7816,0.0560, 0.1109,0.7316,0.5988,0.0174,0.0255,0.8042,0.6785,0.0685,0.8624,0.4913, 0.3914,0.6016,0.6013,0.4869,0.4036,0.7793,0.6142,0.4322,0.5552,0.0047,

Daniel Bengtson on 23 Aug 2023
Edited: Daniel Bengtson on 23 Aug 2023
You can use fprintf to do that.
fid1 = fopen('filename.csv', 'w');
fprintf(fid1,'%.4f',0.999763425634234234);
Gerrit on 24 Aug 2023
Thank you: However, if I use this fprintf function witht eh simple formatting '%.4f' only, all elements in the matrix are strung together into one string instead of forming a matrix in the csv file:
matrix3 = rand(2,3)
matrix3 = 2×3
0.3781 0.9722 0.5639 0.6576 0.4597 0.3789
fid1 = fopen('table3.csv', 'w');
fprintf(fid1, '%.4f', matrix3);
fclose(fid1);
The only value/string in the resulting csv file is (this was from execution in my own Matlab, so the numerical values are different):
0.96490.15760.97060.95720.48540.8003
i.e. six values in '%.4f' format, but all in one single string. If I use instead, for the fprintf line:
fprintf(fid1, '%.4f %.4f %.4f\n', matrix3);
I get two rows/fields above each other in the csv file:
0.9649 0.1576 0.9706
0.9572 0.4854 0.8003
So still not in a comma-separated format that I can import/transfer directly to a Word table. Ah, I now see Voss's answer below including the 'repmat' function to do the matrix/table formatting. Yes, that works. I'll still post my comment here in case it helps anyone else.

Walter Roberson on 23 Aug 2023
For the case of a text file, dlmwrite supports a Precision parameter that can be number of digits or can be a format specification.
Gerrit on 24 Aug 2023
Thank you. Your solution would address my issue as well. However, the Matlab help specifically dissuades the use of this function:
It is a pity that a function, dlmwrite, with more (formatting) options is replaced by one with fewer such options, i.e. writematrix. I notice that "There are no plans to remove dlmwrite.", but the 'not recommended' is still a bit off-putting.

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