How do I export the calculations of a textfile?

I have to export to a file all the values of variables X and Y.

A = 10:0.1:100;
B = 100:1:1000;
C = 1:0.01:10;

X = A .* B;
Y = (A ./ B) .* C;

i.e. the X and Y values for each value of A, B and C. I've tried with

M = [ X ; Y ];
nomefile = fopen ( 'FILE.txt' , 'a');
fprintf ( nomefile , '%16.15E %16.15E\r\n' , M );
fclose (nomefile);

but I got a mess. I was supposed to get a file with 7.29E+08 lines, but I got a much smaller file with wrong values. Thank you!

[Star Strider]

Do you have any restrictions on how you have to do it?

I would be tempted to use the dlmwrite function.

[Adam]

What do you get if you just pass X and Y as two separate arguments to fprintf instead of merging them into M?

[Eneru Y]

I must get the values of X and Y in two columns, for example:

1.000000000000000E+03 1.000000000000000E+03
1.010000000000000E+03 1.010000000000000E+03
1.020000000000000E+03 1.020000000000000E+03 
[...]

[Stephen23]

"I was supposed to get a file with 7.29E+08 lines"

The variables X and Y each have exactly 901 elements (values) in them. How do you expect to get 7.29e8 lines from just 901 pairs of values ?

[Eneru Y]

So to be precise:

A .* B = 901 * 901 values = 901² = 811801 values
(A ./ B) .* C = 901 * 901 * 901 = 901³ = 731432701 values

Thus X column = 811,801 rows and Y column = 731,432,701 rows.

[Stephen23]

"Thus X column = 811,801 rows and Y column = 731,432,701 rows"

Nope, not even close:

>> size(X)
ans =
     1   901
>> size(Y)
ans =
     1   901

If you want matrix multiplication then you need to use the correct operator. If you want all permutations then use bsxfun, although you will likely run out of memory.

[Walter Roberson]

Using ndgrid or bsxfun runs out of memory on my machine.

Also, 901*901 is odd, so it is not clear how one would write it out as two columns? Two in which order? Should the last of the rows have only one entry?

Answer 1

[Eneru Y]

I think I found the solution:

for A = 10:0.1:100
    for B = 100:1:1000
        for C = 1:0.01:10

          X = A * B;
          Y = (A / B) * C;

          U = [ X ; Y ];
          fid = fopen('FILE.txt','a');
          fprintf(fid,'%16.15E %16.15E\r\n', U );
          fclose(fid);
          end
      end
  end

This way it works. Thanks anyway!

[Stephen23]

It would be much better to open the file before and after the loop, use w to write to a cleared file, and use the t option (because this handles newlines correctly):

fid = fopen('FILE.txt','wt');
for ...
    ....
    fprintf(fid,'%16.15E %16.15E\n', U );
end
fclose(fid);

[Eneru Y]

Thank you!