Why do I get NaNs when I try interpolating with interp1?

I am using interp1 to interpolate my data. But, the function is creating NaNs at the end of my query points (last 2000 points).

interp_co2 = interp1(clean_time_co2, clean_co2, time_common); 

I have attached clean_time_co2, clean_co2, time_common, and what my computer has as interp_co2. My original data doesn't have any NaNs, but the interp_co2 does have NaN values, and I don't know why.

Thank you!

Answer 1

[Star Strider]

It will do that if you atempt to extrapolate without telling interp1 how you want to do it.

Try this —

interp_co2 = interp1(clean_time_co2, clean_co2, time_common, 'linear','extrap'); 

Choose the appropriate interpolation method. (The default is 'linear' so I assume the same extrapolation method.)

Of course, always be careful about extrapolating, because that assumes knowledge about what the data do beyond the region-of-fit that may not be accurate.

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[Emma Reddy]

That makes a lot of sense, thank you!

[Star Strider]

My pleasure!

(That’s just how the interp# functions work.)

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