How I do a Linear extrapolation?

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Paulo Oliveira
Paulo Oliveira 2014-5-15
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
  2 个评论
José-Luis
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
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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Star Strider
Star Strider 2014-5-15
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')
produces:
xm =
1. 2 3 4
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Anwaar Alghamdi
Anwaar Alghamdi 2022-11-24
编辑：Anwaar Alghamdi 2022-11-24
@Star Strider Does this work if I have missing hourly temperature values? (not NaN but 999)
One or two missing values is fine but if a have a whole day missing? Can this preserve the behavior of hourly temprature profile within the day?
Star Strider
Star Strider 2023-4-29
@Anwaar Alghamdi — I just now saw this.
It depends on what the data are and where the values are that are NaN. The fillmissing function would likely be most appropriate.

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