How I do a Linear extrapolation?

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Paulo Oliveira 2014-5-15

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评论： Star Strider 2023-4-29

Hi, I have a matrix with 160 numbers, but the first values is nan. How I complete this matrix? Anyone help me? I try the -- interp1 --- but I have only a matrix, I do not have a vector to realize the extrapolation.

Thank you for your attention. Best wishes, Paulo Oliveira

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José-Luis 2014-5-15

Extrapolation is tricky business. Depending on the sort of data different extrapolation methods might be warranted. The closest value? A linear interpolation from the first two points. A cuadratic function using the last three points? A spline of n degree?

Extrapolation caused the crash of the Challenger.

Paulo Oliveira 2014-5-15

I understand your questions, but as I said, I have 160 values, but 40 are NAN, so I have a 140 values to support,for you what the best way to do the data extrapolation?

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Answer 1

Star Strider 2014-5-15

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This works:

% Original vector: 
x = 1:10
% Replace the first 4 elements with ‘NaN’: 
x(1:4) = NaN
% Create empty elements for the ‘NaN’ elements: 
x(isnan(x)) = []
% Extrapolate to fill the empty elements: 
xm = interp1(x, -3:0, 'linear', 'extrap')