Trying to write on .csv file, but every time I add something it cancels the previous stuff even if I put it in an empty space

I am doing a series of operations between elements of two columns. I would like to write the result on the same .csv file but when I do it it cancels all the data that was previously on the document. Moreover I am doing the operations through a for loop and writing the result through the same for statement, so at the end all I get is the result of the last operation and everything else is empty. This is what I have:

for x = 1:len
a1 = data(x, col1);
a2 = data(x,col2);
result = a1 + a2;
csvwrite('file.csv', result, x,19) %where 19 is the column I want the results to be in.
end

I am sure there must be a way, but can't seem to find it.

Thanks

[Stephen23]

"I am sure there must be a way"

Not using csvwrite, but you can write your own function using fopen, fprintf, and fclose.