find x intercepts numerically

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Elizabeth Ramsey
Elizabeth Ramsey el 25 de Mayo de 2020
Comentada: Elizabeth Ramsey el 25 de Mayo de 2020
I'm trying to find a quick way of returning the index of all the places where an [x,y] data set crosses the x axis.
I've tried: zci = @(v) find(v(:).*circshift(v(:), [-1 0]) <= 0)
But it isn't returning all the zeros and also always returns the last value in my dataset as a zero even though it isn't. I'm testing with a third order polynomial and can only get my code to work if it have only one root.
Thanks!

Respuesta aceptada

Ameer Hamza
Ameer Hamza el 25 de Mayo de 2020
Editada: Ameer Hamza el 25 de Mayo de 2020
Try this
f = @(x) find(diff(sign(x)));
Example
>> x = [1 2 -1 -2 -1 2 3 1 -2 -3 -2 1];
>> f(x)
ans =
2 5 8 11
  1 comentario
Elizabeth Ramsey
Elizabeth Ramsey el 25 de Mayo de 2020
Exactly what I needed, thanks so much!

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