2D general polynomial fit

[altenbach]

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@paul_a_cardinale wrote:

I wrote this many years ago.  You might find it helpful.

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Did you ever implement it in LabVIEW?

[sasko]

Thank you for reply.

I substracted a mean value from Z. You are right that the error is small in the middle but is about 30% at the edges and it seems to me that it should/must be much better.

I'v done also polynomial fitting with your functions.

polinomial fitting work fine for this measured points but sometimes I can not fit easily some measurement.

I thought that griddata can work much better, specially for low N, since I need to send this interpolation point to EEPROM and have good accuracy of my device.

I attach a VI.

If you have more comment you are welcome.

Regards

Sasa

[paul_a_cardinale]

Here it is.  I haven't looked at this in a long time; don't remember if it had any quirks.

[ElenaP]

hello again, i know its been 5 years from your last post

but i would like to ask you about the  3DPolyFiArrayOutput VI  how can i adapt it to a 2d array version with random numbers. ( i have changed the dimensions of the array and the intensity graph axis)  but i only get a blank graph ....

here it is my vi with changes..

thanks in advance!

[altenbach]

As a first step, place indicators on all error output. You would immediately see that the general linear fit produces the following error:

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Error -20037 occurred at an unidentified location

Possible reason(s):

Analysis: (Hex 0xFFFFB1BB) The number of data points in the Y value array must be greater than the order value.

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For a second order 2D fit, you need at least 6 rows of data, so increase N of the outer loop accordingly.

[ElenaP]

hello again

can you tell me altenbach for this bilinear interpolation subvi which mathematical equation did you use ?