location zero crossings of the signal

The following program produces sine signal plus noise. I have to write a function(Call zero crossing function that you see in the code below) in MATLAB to identify location zero crossings of the signal,found the locations where Signal changes sign.

clc
clear all
close all
N=1000;   %Number of samples 
n=0:N-1;  % Sample index
Ts=0.0025; %Sample interval
f1=2; %freq=2Hz

%Generate signal+noise
x=0.5*sin(2*pi*f1*n*Ts+pi/4)+0.01*randn(size(n));

*_%Call zero crossing function
I=find_zero_cross_fnc(x);
s=zeros(size(I));_*

% Plot results
figure
stairs(x,'Linewidth',1), hold on
stem(I,s,'*r','Linewidth',3)

[Wayne King]

So what are you asking from us?

[Roman]

function(zero crossing) that identify location zero crossings of the signal,found the locations where Signal changes sign.

[John Petersen]

See my answer below.

Answer 1

[John Petersen]

You could let this be your zero crossing function.

zind = diff(x>0);