while loop not ending, juz stopped at i = 3

Hi, I am new to Matlab.

I wrote a below script to get the vector fwd = [3 8]. If I put breakpoints I could see the fwd I want. but the code never ended.

Could anyone please point out the mistake? thanks in advance!

clc; clear; close all
a = [1 2 3 4 2 3 4 5 6 3 4 5 6 8 9 10 9 8 7 6 7 8 9 8 7 5 4 3 2 4 5 3 2 1];
start = min(a)+2;
ed = max(a) -2;
m = length(a);
f = 1; 
i = 2;
while i < m
    if a(i) >= start && a(i-1) <= start && a(i+1) > a(i) 
        fwd(f,1) = a(i);
        for j = i+1:m-1
            if a(j+1) > ed && a(j+2) >= a(j+1) && a(j) < a(j+1)
                fwd(f,2) = a(j);
            end
        end        
        
    else
        i = i+1;
    end
end

Answer 1

[Bjarke Skogstad Larsen]

In your code, once the following is true, it is always true, since you don't modify any of the variables inside the 'if'

if a(i) >= start && a(i-1) <= start && a(i+1) > a(i)    

Thus, your variables i and m stay the same after this point, and you get stuck in an infinite loop.

Maybe you intended i to increase after each iteration regardless of the 'if'?

In this case, the following should work, though it doesn't result in the result you say is correct: [3 8]

while i < m
    if a(i) >= start && a(i-1) <= start && a(i+1) > a(i) 
        fwd(f,1) = a(i);
        for j = i+1:m-1
            if a(j+1) > ed && a(j+2) >= a(j+1) && a(j) < a(j+1)
                fwd(f,2) = a(j);
            end
        end
    end
    i = i+1;
end

It's difficult to get any closer to solving this without any explanation of what your code is supposed to do.

[HYZ]

Thank you. I revised my code based on your advice. now it's solved.

clc; clear; close all
a = [1 2 3 4 2 3 4 5 6 3 4 5 6 8 9 10 9 8 7 6 7 8 9 8 7 5 4 3 2 4 5 3 2 1];
start = min(a)+2;
ed = max(a) -2;
m = length(a);
f = 1; r = 1;
i = 2;
while i < m
    if a(i) >= start && a(i-1) <= start && a(i+1) > a(i) 
        fwd(f,1) = a(i);
        for j = i+1:m-1
            if a(j+1) > ed && a(j+2) >= a(j+1) && a(j) < a(j+1)
                fwd(f,2) = a(j);
            end
        end        
        i=j+1;
    else
        i = i+1;
    end
end