MATLAB: Doesn´t it stop the loop

if loop

Hi everybody,

I have a probably pretty stupid question, but I have no Idea what my problem is here.

In the following Code I was trying to say if whatever is in the if codition is true, don´t advance checking if the condition is true in the next loop. So I was trying to escape the loop by saying If it is true one time, set huellkoerper=4 to end the inner for loop.

Thing is now. If one of the points described by allepunkte fullfills the condition in the If-Condition, it shouldn´t further check in the upcoming huellkoerper.

Anyway, if I let it run it tells me this:

That point 4 and eight are both inside body 1 and 2. This is right, but my goal is not to count twice. So if anything is Inside Body 1, don´t check for body 2. If something is in body 2, don´t check for body3. Why does it do so in this case? Why doesn´t the programm escape the inner for loop?

I´m so glad for any advice or help. Thank you guys a lot in advance!

Johnny

Best Answer

use break instead. You should never try to change the loop variable.

break;

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MATLAB: Matlab wont plot anything

You have

n=1:25
while n<26
R(n+ 1) = -0.8*R(n);
end

After the first statement, n is a vector of 25 values. The n<26 in the next line is then comparing that vector of 25 values to the value 26. It happens that all of them are less than 26 so the result of the < is a vector of 25 "true" (1) values. When you use "if" or "while" with a vector or array of values, "if" or "while" consider the condition to be true if all of the values are non-zero, which they are in this case (being all true which is 1). So the test in the while is satisfied and the loop body is entered.

In the first execution of the loop body, since n is 1:25, you are doing the equivalent of

R((1:25)+1) = 0.8*R(1:25)

which is

R(2:26) = 0.8*R(1:25)

you have 25 values on the right side and 25 output locations on the left, so the assignment is well defined. This will extend R (which you defined as length 25) to being length 26. This will not change n in any way.

You then reach the end of the while loop, and you go back up to the test while n<26. n has not changed at all, so the test is still true, and R(2:26) = 0.8*R(1:25) is done again. And then it loops back and n has not changed so n<26 is still completely true and R(2:26) = 0.8*R(1:25) is done again, and so on. n never changes so n<26 never changes and the loop never ends. You never get back the >> prompt because the "while" is still executing.

You should be using a for loop:

R = zeros(1,26);
R(1) = -80;
for n = 1 : 25
  R(n+ 1) = -0.8*R(n);
end

MATLAB: Do I get this error? If i do it in the command window it seems to be possible

Inside a for loop, you are assigning

M = M{INDEX}

That replaces all of M with the contents of one cell of M. Afterwards, M is unlikely to be a cell array.

Best Answer

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