Interp1 returns NaN for a value
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I have some data (x,f(x)) where 0<=x<=1 and I have N points. I wish to obtain f for an inteverval [a,b] which is well within the limits of 0 and 1, and on my end point, I get a NaN so some reason. I think my data set goes up from 0.001 to 0.999, and the set I want values for goes between 0.05 and 0.96. There is no extrapolation required.
What's going on exactly?
9 个评论
dpb
2019-10-8
Show us the data and code...we can't guess.
Matthew Hunt
2019-10-8
dpb
2019-10-8
Then we really can't do much to help...your problem is data-specific
Matthew Hunt
2019-10-8
dpb
2019-10-8
It's not that we're "unwilling" but if we can't reproduce an unspecified problem, what are we supposed to do? Buy the Crystal Ball Toolbox?
I be surprised if putting a set of x,y data into a .mat file and attaching it with no identifying info or context could possibly be of any real impact to your organization.
Or, if you wish, contact me directly thru my link thru the ML Contributors link and I'll destroy anything received once the issue is resolved one way or another.
Sciora Chang
2021-10-25
Have you solved this problem? I have met the exact same situation and couldn't figure out why.
dpb
2021-10-25
As we told the original poster some two years ago, unless you post the data and the code, there's nothing can do beyond the general suggestions given here then -- interp1 has been around long enough that if there were some actual flaw in it, it is highly unlikely it wouldn't have been found long before now.
Attach the data at a minimum...
Michael Demkowicz
2023-11-21
I've run into the same problem: interp1 returns a NaN at the endpoint of the interpolation range. I'm attaching the data to demonstrate the problem. I see NaN when I load the data and run the following commands:
nirrhor=interp1(irr,irrhor,r);
nirrhor(length(r))
"I've run into the same problem: interp1 returns a NaN at the endpoint of the interpolation range. I'm attaching the data to demonstrate the problem. I see NaN when I load the data and run the following commands"
Lets take a look:
S = load('interpdata.mat')
V = interp1(S.irr,S.irrhor,S.r)
X = find(isnan(V))
fprintf('%.42f %.42f\n', S.r([1,X]), S.irr([1,end])) % requested; supplied
The last value you requested clearly lies outside the domain of your data. It is unclear what the problem is, everything seems to be working exactly as documented and expected.
回答（2 个）
Star Strider
2019-10-8
1 个投票
You could have NaN values in your data. If so, first use the fillmissing function (R2016b and later reseases), then interp1.
2 个评论
Matthew Hunt
2019-10-8
Star Strider
2019-10-8
If you are not extrapolating (that should only produce NaN values for the extrapolated values if you do not include a method designation and the 'extrap' argument), and there are no NaN values anywhere in your data, and we can’t see your data to test it, this will likely remain unsolved.
Chris B
2022-8-27
移动：Image Analyst
2022-8-27
I ran into an issue where my start and endpoints were NaN. Turns out I was defining my x and xquery values differently. For example, try this code:
x=[500:2:1100]*10^-1;
xq=[500*10^-1 :2*10^-1: 1100*10^-1];
x==xq
x ~= xq because you are comparing floats in this case. Change 10^-1 to 10^1 and you'll get x==xq. So if you're getting NaNs, try making your x and xquery both integers and then dividing to get floats afterward.
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