using interp1 'nearest' and 1 value is missing

Question

Roy Azami 2020-8-7

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https://ww2.mathworks.cn/matlabcentral/answers/576373-using-interp1-nearest-and-1-value-is-missing

评论： Roy Azami 2020-8-7

hey,

i have 2 datetime arrays and im trying to find the nearest date and time (prior) from one array to another using interp1

my line of code is:

nearest= interp1(refDatetime, 1:length(refDatetime),expDatetime, 'nearest');

refDateTime:

'03-Feb-2020 09:28:38'	'03-Feb-2020 10:49:51'	'03-Feb-2020 11:02:04'	'03-Feb-2020 11:04:18'	'03-Feb-2020 11:17:35'	'03-Feb-2020 11:20:28'	'03-Feb-2020 11:25:41'

expDatetime:

'03-Feb-2020 11:22:39' '03-Feb-2020 11:28:40'

nearest:

6 NaN

interp1 always gives me NaN for the last exp date time (i run the code with several inputs giving different values for these 2 arrays).

the value i expect is 7 but instead its NaN

any idea what i do wrong?

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Answer 1

Walter Roberson 2020-8-7

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https://ww2.mathworks.cn/matlabcentral/answers/576373-using-interp1-nearest-and-1-value-is-missing#answer_476347

在 MATLAB Online 中打开

nearest= interp1(refDateTime, 1:length(refDateTime),expDateTime, 'nearest', 'extrap')

The interpolation mode you were using, linear interpolation (the default) returns nan for anything outside of the range of the input independent variable; you have to turn on extrapolation.