# LabVIEW

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## cubic hermite

Hello,

LV Help states that Interpolate 1D.vi, used with the Cubic Hermite method, should give the same results as Hermite Interpolation 1D.vi. However, I find a problem with the latter as soon as the spacing of the Xi is non-equidistant.

I have attached an example of simple monotonic curve to be interpolated. A "swap" button allows on the swap X and Y, by that making the Xi non-equidistant. As a result, the first VI still does the job, while the second completely goes off track.

Can anyone explain to me what I am doing wrong, or is it a bug?

The real-life application is that I would like to take a calibration curve, let's say wavelength vs. motor position and use these VIs in both direction for readout (position -> wavelength) and control (requested wavelength ->position). For speed I wanted to use pre-calculated piecewise polynomials of the Hermite Interpolation 1D.vi.

Thank you,

Dirk

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## Re: cubic hermite

Hello Dirk,

thank you for posting this problem. You're right it's a bug. Actually the "Hermite Interpolation 1D.vi" should give the same solutions as the "Interpolate 1D.vi" in the cubic Hermite mode like the help says.

Regards,

Stefan Stangl

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## Re: cubic hermite

@Steve'O wrote:

Hello Dirk,

thank you for posting this problem. You're right it's a bug. Actually the "Hermite Interpolation 1D.vi" should give the same solutions as the "Interpolate 1D.vi" in the cubic Hermite mode like the help says.

Regards,

Stefan Stangl

Could you please post the CAR number for that bug?

Ben

Retired Senior Automation Systems Architect with Data Science Automation LabVIEW Champion Knight of NI and Prepper LinkedIn Profile YouTube Channel
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Accepted by topic author Dirk@LV

## Re: cubic hermite

Sry Ben, forgot 🙂

CAR number: #372390