how can I write two matrix into the same csv file

I'm trying to write two matrix into csv file using writematrix I tried to speart them with line as divider in the file but I couldn't do that I just want them to be in the same file but add headline or something to indicate which one is matrix a and b

so the file will be something like this (or next to each other)

a

1 4 9

16 25 36

49 64 100

b

1 4 9

16 25 36

49 64 100

how can I do that with writematrix?

a = [ 11    12    13;
    14    15    16;
    17    18    20]
 
 
b= [  1     4     9;
    16    25    36;
    49    64   100]
writematrix(a,'a.csv','Delimiter','tab');
writematrix(b,'a.csv','Delimiter','tab');

Answer 1

[dpb]

There's nothing in the documentation for writematrix that should have led you to think you could possibly do what you're asking with it.

It writes a matrix to a text or spreadsheet file but nothing is mentioned about having any header information or other than a homogenous matrix as an input and there are no optional named arguments that provide a naming facility nor, even, the ability to append to a file.

To do what you wish to do precisely, you would first open a file using fopen returning a file handle, write the formatted text with fprintf followed by writing the array. There you could possible use csvwrite with the append option. Then, "rinse and repeat" for the second array and close the file.

Alternatively, since your two arrays are commensurate in size, you could convert to a table and then use writetable which will identify variables in the table by column.

If the intent/need is to just have a way to save/recover a set of variables form the workspace and not to have text files for visual inspection and editing or some similar purpose, then the simplest way is to use the builtin Matlab storage facility of a .mat file --

save ab.mat a b
...
load ab

You can see whos in the .mat file with whos

>> whos -file xy.mat
  Name          Size            Bytes  Class     Attributes

  x2        10000x1             80000  double              
  y2        10000x1             80000  double              

>> 

for an example just laying around here...

Answer 2

[Mohammad Farhad Aryan]

If you are using Matlab 2019, you could use the following recommended function to write a matrix to a set of files.

writematrix(a,'a.csv');
writematrix(b,'a.csv','WriteMode','append');

But there is no option to add a separator line or headline in between.

If you want to read the .csv file, use the following function.

a_file = readmatrix('a.csv');

Hope this can help.