For loop to write in Excel file

Hi I have a problem with for loop and xlswrite statements. Actually I want to have a nested loop like this:

fid = fopen ('data1.xlsx', 'r');
fid = fopen ('reg1.txt', 'w');
for i = 1:4
  x = data1(:,i);
  for j = 2:5
      y = data1(:,j);
      p = polyfit(x,y,1);
      yfit = polyval(p,x);
      yresid = y - yfit;
      ssresid = sum(yresid.^2);
      A = ([i; j; ssresid]);
      reg1 = xlswrite('reg.xlsx', [i, j, ssresid]);
  end
end  
and write the results of all iterations in Excel. However, I don't know how I can do this. The above code can just write the last iteration on the Excel file that it doesn't work for me. I want to have all iterations. 
It would be great, If you can help me.
Thanks in advance

Answer 1

[Rafal Samborski]

This one should work:

fid = fopen ('data1.xlsx', 'r');
fid = fopen ('reg1.txt', 'w');
A = [];
for i = 1:4
  x = data1(:,i);
  for j = 2:5
      y = data1(:,j);
      p = polyfit(x,y,1);
      yfit = polyval(p,x);
      yresid = y - yfit;
      ssresid = sum(yresid.^2);
      A(:,end+1) = ([i; j; ssresid]);
  end
end
reg1 = xlswrite('reg.xlsx', A);

[Vahid]

Thanks Rafal!

It works.

You did best.