# if statement didn't executed in a loop

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Shawn Chang on 13 Dec 2012
Hi all, I have problem on the if statement that inside can't be executed which makes other operations in the code cannot be run. My code is as follow, the problems is occurred at the "if isequal(time(i),off_tt)" parts where the variables 'k' didn't increment.
k = 0; on_t = 2;off_t = 2;
for i=1:length(time)
on_tt = (on_t*(k+1))+(off_t*k)
off_tt = (on_t*(k+1))+(off_t*(k+1))
if(time(i) ~= off_tt)
if (on_t == 0)
ref_speed_left = [ref_speed_left, 0];
ref_speed_right = [ref_speed_right, 0];
elseif (off_t == 0)
ref_speed_left = [ref_speed_left, ref_speedR];
ref_speed_right = [ref_speed_right, ref_speedL];
elseif (time(i) < on_tt) %ans == 0
ref_speed_left = [ref_speed_left, ref_speedR];
ref_speed_right = [ref_speed_right, ref_speedL];
elseif (time(i)>= on_tt && time(i) < off_tt+1)
if isequal(time(i),off_tt) %problems at this if statement
k=k+1; %k didn't increment when it
end %met the requirement
ref_speed_left = [ref_speed_left, 0]
ref_speed_right = [ref_speed_right, 0]
end
end
end
May I know any solutions for this, your helps is much appreciate. Thanks you.
##### 2 CommentsShowHide 1 older comment
Shawn Chang on 13 Dec 2012
Edited: Shawn Chang on 13 Dec 2012
time = 0.05:0.05:14.95;
ref_speedR = 0.3595;
ref_speedL = 0.3693;

Ilham Hardy on 13 Dec 2012
for i=1:length(time)
k=i %correction
on_tt = (on_t*(k+1))+(off_t*k)
off_tt = (on_t*(k+1))+(off_t*(k+1))
You declare k=0, therefore k is 0.
##### 1 CommentShowHide None
Shawn Chang on 13 Dec 2012
"k=0" is used to initialize the k.
When on_tt and off_tt value has been met and k will be increment by 1 to obtain a new on_tt and off_tt.
eg. last value in time(i) = 15, on_t = 2, off_t = 2;
When k = 0; on_tt = 2, off_tt = 4;
When k = 1; on_tt = 6, off_tt = 8;
until either on_tt or off_tt reached 15, it will break the for loop.
So, "k=i" cannot be used in this case

Azzi Abdelmalek on 13 Dec 2012
Edited: Azzi Abdelmalek on 13 Dec 2012
Are you sur the condition if isequal(time(i),off_tt) is true? I tested your code, the condition is true only for i=80
Azzi Abdelmalek on 13 Dec 2012
you have then to revise your code

Roger Stafford on 13 Dec 2012
Shawn, look at the third line from the beginning of the for-loop:
if(time(i) ~= off_tt)
It is an outer condition that must be satisfied if you are to enter the if-elseif-elseif-end sequence. This means you cannot reach the
if isequal(time(i),off_tt)
test with equal values of time(i) and off_tt. Hence the 'isequal' test will always be false and k can never be incremented.
I am curious as to why you used 'isequal' at that point. It is intended for testing equality between entire arrays and suggests that you may have meant something else in your code here.
Roger Stafford