for - for loop to repeat specified number

of times - MATLAB (original) (raw)

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 by1, 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.

example

Examples

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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

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

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

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

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

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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. SeeResolve Error: Cannot Determine the Exact Number of Iterations for a Loop (MATLAB 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 offor statements. Instead, use theall orany functions to collapse logical vectors into scalars.

Version History

Introduced before R2006a