for

for loop to repeat specified number of times

Syntax

for index = values
   statements
end

Description

for index = values, statements, end executes a group of statements in a loop for a specified number of times. values has one of the following forms:

• initVal:endVal — Increment the index variable from initVal to endVal by 1, and repeat execution of statements until index is greater than endVal.

• initVal:step:endVal — Increment index by the value step on each iteration, or decrements index when step is negative.

• valArray — Create a column vector, index, from subsequent columns of array valArray on each iteration. For example, on the first iteration, index = valArray(:,1). The loop executes a maximum of n times, where n is the number of columns of valArray, given by numel(valArray(1,:)). The input valArray can be of any MATLAB^® data type, including a character vector, cell array, or struct.

Examples

Assign Matrix Values

Create a Hilbert matrix of order 10.

s = 10;
H = zeros(s);

for c = 1:s
    for r = 1:s
        H(r,c) = 1/(r+c-1);
    end
end

Decrement Values

Step by increments of -0.2, and display the values.

for v = 1.0:-0.2:0.0
   disp(v)
end

     1

    0.8000

    0.6000

    0.4000

    0.2000

     0

Execute Statements for Specified Values

for v = [1 5 8 17]
   disp(v)
end

     1

     5

     8

    17

Repeat Statements for Each Matrix Column

for I = eye(4,3)
    disp('Current unit vector:')
    disp(I)
end

Current unit vector:

     1
     0
     0
     0

Current unit vector:

     0
     1
     0
     0

Current unit vector:

     0
     0
     1
     0

Tips

• To programmatically exit the loop, use a break statement. To skip the rest of the instructions in the loop and begin the next iteration, use a continue statement.

• Avoid assigning a value to the index variable within the loop statements. The for statement overrides any changes made to index within the loop.

• To iterate over the values of a single column vector, first transpose it to create a row vector.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• Suppose that the loop end value is equal to or close to the maximum or minimum value for the loop index data type. In the generated code, the last increment or decrement of the loop index might cause the index variable to overflow. The index overflow might result in an infinite loop. See Loop Index Overflow (MATLAB Coder).

• When the number of for-loop iterations calculated by the generated code does not match the number of for-loop iterations calculated by MATLAB, the generated MEX function produces an error at run time. See Resolve Error: Cannot Determine the Exact Number of Iterations for a Loop (MATLAB Coder).

HDL Code Generation

Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.

• Do not use for loops without static bounds.

• Do not use the & and | operators within conditions of a for statement. Instead, use the && and || operators.

• HDL Coder™ does not support nonscalar expressions in the conditions of for statements. Instead, use the all or any functions to collapse logical vectors into scalars.

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

Version History

Introduced before R2006a