MATLAB: Errors with 32 bit.

32-bitinterp1

Hello,

I have MATLAB's student editin which is 32 bit. I wanted to do linear interpolation by interp1(x,y,xq). My x is a monotonic vector of size 10. The same goes for 7. When I enter and xq between the boundaries of x, it might or moght not give NAN depending on the value. Do you have any idea why it might be giving NAN?

Thank you,

Emre

Best Answer

If xq is outside the intervals defined by x, NaN is replies as corresponding y value. Inside the boundaries, NaN is not replied. Therefore I'm convinced you calculate something other than you think.

Please post an explicit example, which reproduces your problem.

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This behavior was fixed in R2012a. If you are current on SMS, you can download R2012a or R2012b for free.

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If the NaN values were at the leading and trailing (I assume at both ends) of your position-velocity matrix, and you are using the velocities to create your interpolation vector, you are likely extrapolating (or at least interp1 thinks so). See if changing the interp1 call to:

final_data(:,i) = interp1(other_data(:,1),other_data(:,2),x_interp, 'linear', 'extrap');

changes its behaviour. (You might want a different method than 'linear'. There are several to choose from, but if you extrapolate, you must specify a method.) Also, interp1 may not like the NaN values, so deleting the entries that have them may help get your code to work.

If you are still having problems with those changes, it could help if you uploaded a representative subset of the data that worked and the data that failed, along with the relevant part of the code you used in both situations. Did all of them have some NaN values in the velocity column?

Best Answer

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