Condition on zero crossing

Hi everybody,

I need to make an if statement on a zero crossing of an array (composed of n variable). In particular, I need to find when my array crosses the zero and based on that moment make the if statement. For example:

if array == 0 (that states for: when my array crosses zero)
 bla bla bla
else
 bla bla bla
end

(the problem is that in my array there is not a value that corresponds exactly to zero).

P.S. Sorry for my lack of precise information, I'm new in matlab.

Answer 1

[lokender Rawat]

Since you mentioned that there is no single value in the array which equals zero. And you specifically want to do some task when there is a zero crossing and other task when it does not. So I have included a sample script below:

% numZeroCross() will return the number of zero-crossing in the array
% passed as parameter 

function times=numZeroCross(x)
len=length(x);
count=0;
   for i=1:len-1
      if((x(i)*x(i+1)) < 0)
        disp('zero crossing');
        %do something
        count=count+1;
      else
        disp('not a zero crossing');
        %do something
      end
   end
times=count;
end

For example the array has values:

arr = [80.6 120.8 -115.6 -76.1 131.3 105.1 138.4 -81.3-95.3 89.2 -154.1 121.4 -85.1 96.8 68.2]

Call the function from the command window : numZeroCross(arr)

Output will be 8.