Try this:
x=-4:5;
for k = 1:numel(x)
z=x(k).^2;
y(k) = z;
end
[miny,idx] = min(y);
left_x = interp1(y(1:idx),x(1:idx), y(1)/2)
right_x = interp1(y(idx:end),x(idx:end), y(1)/2)
figure
plot(x,y)
hold on
plot([left_x right_x], [1 1]*y(1)/2, '+r')
hold off
There is no ‘full width-half-maximum’ because ther is no defined maximum. This code finds the approximate values for ‘full-width-half-minimum’ instead, since only that makes sense in this context.
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