Add text to string in for-loop

Hi,

I would like to add text to a string in a for-loop.

In the end the string should be: str= X(1)+X(2)+X(3)+X(4)....+X(150).

This is my code:

counter = 1;
for i= 1:150
  if counter == 1
      str= sprintf('  X(%04d) ',i);
  else
      str= sprintf(' + X(%04d) ',i);
  end
  counter= counter + 1;
end

However, this results in str= " +X(150)" only instead of the entire sequence.

Can anyone help me with this?

Answer 1

[Adam]

You need to concatenate( in the else as you currently have it):

str = [str sprintf(' + X(%04d) ',i)];

Why do you have the counter variable though? You already have a loop variable i that can do this. Though personally I would initialise the string with the unique first case outside of the loop. There's no need to test whether you are on the 1st iteration every single iteration of the loop when you know for sure it will only be true the first time. The performance cost is minimal here, but still, you don't want to do things in a loop that don't need to be done in a loop, as general good practice.

[Bas]

Thanks! I actually got more than 1 for-loop, but described only one for simplicity..

Answer 2

[Guillaume]

If you have matlab R2016b, creating your string is extremely easy using the new string class and associated functions compose and join:

str = join(compose('X(%d)', 1:150), ' + ')

just one line!

[Bas]

Thanks! Still didn't got 2016 installed on this desktop..