using interp1 'nearest' and 1 value is missing

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?

Answer 1

[Walter Roberson]

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.

[Roy Azami]

Thanks!! saved my life :)