An interactive introduction to MATLAB

60 loops

15 n = input('Enter the number of terms to sum: ');

16 my_sum = 0;

17 r = 0.5;

18 for m = 0:n

19 my_sum = my_sum + r^m;

20 end

21 format long % Sets display format to 15 digits

22 my_sum

Comments:

• Line 15 contains theinputcommand, which is used to get the number
  of terms to be summed from the user.


• On Line 16 a variablemy_sumis created (and set to zero) to hold the
  sum of the geometric series. It is necessary to create any variables outside
  of loops before using them within loops.


• Lines 18–20 contain theforloop. The loop countermcounts in steps of
  one from zero until the number of terms specified by the usern.


• On Line 19 (the body of the loop) the new term in the sumr^mis
  added to the previous value ofmy_sumand this becomes the new value
  ofmy_sum.


• Lines 21–22 display the result of the summation. Theformatcommand
  is used to set the display to 15 digits instead of the default 4 digits so
  that the result of taking more terms in the summation can be seen.

5.2 while loops

Awhileloop is similar toforloop in that it is used to repeat a command,

or set of commands. Listing 5.4 shows the syntax of awhileloop. The key

difference between aforloop and awhileloop is that thewhileloop will

continue to execute until a specified condition becomes false.

Listing 5.4: Syntax of awhileloop

1 whilecondition is true

2 statements

3 end