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Can I change the loop size inside the loop?

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sakib shalehin
sakib shalehin on 16 Apr 2018
Edited: Stephen Cobeldick on 16 Apr 2018
for i=1:s
statements
end
here,can i change the value of s inside the loop.

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Answers (1)

David Fletcher
David Fletcher on 16 Apr 2018
Edited: David Fletcher on 16 Apr 2018

For loop conditions are set upon entering the loop and the only form of modification that can be made is to 'break' out of the loop early. If you need a indeterminate loop duration use a while loop where the loop condition is checked upon every iteration. From the for loop docs:

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

Although this only explicitly mentions the loop index variable, it also extends to the end counter:

s=5;
for iter=1:s
    iter
    s=3;
end

>> test

iter =

     1

iter =

     2

iter =

     3

iter =

     4

iter =

     5

As can be see, the attempt to assign 3 to the loop end condition has been ignored

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