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Error when calling function

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Ejay Nsugbe
Ejay Nsugbe on 9 Jul 2019
Answered: Geoff Hayes on 9 Jul 2019
Im trying to calculate the 'Zero Crossings' in a sample signal with the below code.
When I try calling the function in the command window using 'zc = ZeroCrossing(t,emg6);' i get an error that says "Attempt to execute SCRIPT ZeroCrossing as a function."
I'd be grateful if someone can shed some insight on this.
Fs=200;
samples=0:2186; %number of data points in matrix
t = samples/Fs; % Time Vector (seconds)
t(:,[1]) = [];
function zc_idx = ZeroCrossing(t,emg6)
zci = @(v) find(v(:).*circshift(v(:), [-1 0]) <= 0);
zx = zci(emg6);
zc_idx = zeros(numel(zx),1); % initialise the zero crossing indices
for i = 1:numel(zx)
idx = max([1 zx(i)-1]):min([zx(i)+1 numel(emg6)]);
x_range = t(idx);
y_range = emg6(idx);
zc_idx(i) = interp1( y_range(:), x_range(:), 0, 'linear', 'extrap' ); % returns the approximate zero crossing Indices of argument vector
end
end

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Accepted Answer

Geoff Hayes
Geoff Hayes on 9 Jul 2019
Ejay - see Scripts vs Functions to understand the differences between scripts (which you have written) and function (which you want to write). Since the first line of code (in the above) is neither a comment nor a function signature, then MATLAB assumes that you have written a script. You need to change your code so that the first line is the signature
function zc_idx = ZeroCrossing(t,emg6)
zci = @(v) find(v(:).*circshift(v(:), [-1 0]) <= 0);
zx = zci(emg6);
zc_idx = zeros(numel(zx),1); % initialise the zero crossing indices
for i = 1:numel(zx)
idx = max([1 zx(i)-1]):min([zx(i)+1 numel(emg6)]);
x_range = t(idx);
y_range = emg6(idx);
zc_idx(i) = interp1( y_range(:), x_range(:), 0, 'linear', 'extrap' ); % returns the approximate zero crossing Indices of argument vector
end
end
The code
Fs=200;
samples=0:2186; %number of data points in matrix
t = samples/Fs; % Time Vector (seconds)
t(:,[1]) = [];
should be used either in the body of the function or outside of the function (where you need to define the input parameter t).

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