3-d order derivative
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Dear all,
there is the following problem with the calculation of a 3-d order derivative.
I have two vectors of lambda and refractive index, respectively. I take the 3-d order derivative using a gradient().
dndl=gradient(n)./gradient(lambda);
d2ndl2=gradient(dndl)./gradient(lambda);
d3ndl3=gradient(d2ndl2)./gradient(lambda);
When I use a relatively small number of points (for example 3000) , I get a smooth plot.
In the case of more points (30 000) there is some oscillation in the plot.
What is the reason of such behavior?
Thank you a lot.
2 个评论
Matt J
2022-2-13
What do you mean by "use more points"? If it's a different input array why expect the same results?
Max Demesh
2022-2-13
回答（3 个）
Catalytic
2022-2-13
1 个投票
If the points are too close together, the difference between neighbours will be so small as to be dominated by floating point errors
Matt J
2022-2-13
0 个投票
You could try diff(x,3)
2 个评论
Max Demesh
2022-2-14
Matt J
2022-2-14
Why care whether its forward or central? For a smooth curve, it should work out the same.
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2022-2-13
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