for Loop

A for loop has the structure :

    for k = [ list of values of k to be used in the loop ]
        do statements (may use current value of k)  % BODY OF LOOP
    end

The for loop is interpreted as follows:

The variable k is often called a counter or control variable. This variable will take on each successive value of the vector in the first line of the loop. The current value of k can be used inside of the body of the for loop. Any valid variable name can be used for the control variable. Common choices are: i, j, k, and n.

The control flow diagram of a for loop looks like:

The list of values for k can be created using the colon operator. This gives us a convenient way to create a count-controlled loop. The structure of this type of for loop is:

for counter = first : increment : last
    statements  % body of for loop
end

The code first:increment:last creates a vector like the vectors we have created using the colon (:) operator in earlier lessons.

The count-controlled for loop is equivalent (and preferred) to the following while loop:

counter = first;
while counter <= last
    statements  % body of the loop
    counter = counter + increment;
end

We can leave out the increment part of the condition. If we leave it out, Matlab uses an increment of 1. In other words, first:last is equivalent to first:1:last (just as it was when we used the colon operator to create and manipulate matrices).