How can we write data into csv file with column labels included ?

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Mahesh Babu Dhanekula 2020-8-22

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评论： dpb 2022-6-6

I want to write the data into csv file with column labels. I have illustrated the code below.

chead = {'a','b','c','d','e','f','g','h','i','k','l'};
data1 = ones(1001,4);
data2 = ones(125,7);
data = {data1,data2};
R = [chead;data];
writecell(R,'file.csv');

But this doesn't work the way i expected. This was writing the data like:

a b c .......

1 1 1 1 .... 1 1 1 1 .... 1 1 1 1....

instead of

a b c .......

1 1 1

. . .

If anyone knows please tell the answer.

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KSSV 2020-8-22

REad about writetable.

Mahesh Babu Dhanekula 2020-8-22

It doesn't support vectors having variable row length. Can you tell me any workaround method for using this command ?

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Answer 1

dpb 2020-8-22

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编辑：dpb 2020-8-22

在 MATLAB Online 中打开

...
data1 = ones(1001,4);
data2 = ones(125,7);
data = {data1,data2};
...

You have created a disparate-sized array of 125 rows of seven variables and the remainder with only four -- this can't be put into a rectangular array to write a regular .csv file. writecell did what you asked it to do, output the content of the cell array you built; you just didn't build a representation of what you (apparently) intended.

What do you intend the content of the file to be for the shorter records -- missing values or shorter records?

I've not tested if writecell will build a file -- well, let's just see:

>> writecell(cell(2,4))
>> type cell.txt
,,,
,,,
>> 

Ah! Indeed it will, if you convert your numeric array by num2cell to a cell array of one element to cell, and add the empty cells where needed, joy wil ensue.

ADDENDUM:

While it's relatively trivial to write using fprintf, you can try something like

names={'a','b','c'};    % build a set of variable names
writecell(names)        % write to names.txt (pick your name as desired)
c= [ones(2,3) zeros(2,4)];          % longer rows
save names.txt c -ascii -append     % add to existing file
c= ones(2,3);                       % short rows
save names.txt c -ascii -append     % ditto

results in

>> type names.txt
a,b,c
   1.0000000e+00   1.0000000e+00   1.0000000e+00   0.0000000e+00   0.0000000e+00   0.0000000e+00   0.0000000e+00
   1.0000000e+00   1.0000000e+00   1.0000000e+00   0.0000000e+00   0.0000000e+00   0.0000000e+00   0.0000000e+00
   1.0000000e+00   1.0000000e+00   1.0000000e+00
   1.0000000e+00   1.0000000e+00   1.0000000e+00
>> 