How to specify number of decimals in table2word or writematrix

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

https://uk.mathworks.com/matlabcentral/answers/281156-how-can-i-export-a-matrix-as-a-csv-file

).

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.

Answer 1

[Voss]

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,

Answer 2

[Daniel Bengtson]

You can use fprintf to do that.

fprintf

fid1 = fopen('filename.csv', 'w');
fprintf(fid1,'%.4f',0.999763425634234234);

[Gerrit]

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.

Answer 3

[Walter Roberson]

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]

Thank you. Your solution would address my issue as well. However, the Matlab help specifically dissuades the use of this function:

dlmwrite is not recommended. Use writematrix instead. For more information, see Compatibility Considerations.

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.