Programming and Data Types

for

The for loop executes a statement or group of statements a predetermined number of times. Its syntax is:

• for index = start:increment:end
      statements
  end
  

The default increment is 1. You can specify any increment, including a negative one. For positive indices, execution terminates when the value of the index exceeds the end value; for negative increments, it terminates when the index is less than the end value.

For example, this loop executes five times.

• for i = 2:6
      x(i) = 2*x(i-1);
  end
  

You can nest multiple for loops.

• for i = 1:m
      for j = 1:n
          A(i,j) = 1/(i + j - 1);
      end
  end
  

Note    You can often speed up the execution of MATLAB code by replacing for and while loops with vectorized code. See the section "Vectorizing Loops" for details.

Using Arrays as Indices

The index of a for loop can be an array. For example, consider an m-by-n array A. The statement

• for i = A
      statements
  end
  

sets i equal to the vector A(:,k). For the first loop iteration, k is equal to 1; for the second k is equal to 2, and so on until k equals n. That is, the loop iterates for a number of times equal to the number of columns in A. For each iteration, i is a vector containing one of the columns of A.

while

continue