MATLAB: Zero-crossing calculation

zero_crossing

Hi all, I need a script which can calculate zero crossing of the signal. I have the value of x and y. The script should be able to calculate the exact position of zero crossing points. Help!

Best Answer

This is reasonably robust:
function ZC = ZeroX(x,y)
zci = @(v) find(v(:).*circshift(v(:), [-1 0]) <= 0);                    % Returns Approximate Zero-Crossing Indices Of Argument Vector
zxidx = zci(y);
for k1 = 1:numel(zxidx)
    idxrng = max([1 zxidx(k1)-1]):min([zxidx(k1)+1 numel(y)]);
    xrng = x(idxrng);
    yrng = y(idxrng);
    ZC(k1) = interp1( yrng(:), xrng(:), 0, 'linear', 'extrap' );
end
end
x = linspace(0, 11*pi, 42);                                             % Create Data

y = sin(x);                                                             % Create Data
ZC = ZeroX(x,y);
figure(1)
plot(x, y, '-r')
hold on
plot(ZC, zeros(size(ZC)), 'pg')
hold off
grid
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