2D interpolation of non-evenly spaced data

[vituning]

I am trying to use the 2D Interpolation VIs to generate a contour map of my X,Y,Z data much like the 'griddata' function in Matlab. I don't know how to format the Z matrix when I have unevenly spaced data in X or Y. Some rows have more Z data in them than others. The help is a little mistifying, any suggestions?

I have attached a sample data set here. This data is scattered about X and Y, I'd like to generate an ordered 100x100 matrix using the 2D interpolation vis.

Thanks.

[AG123]

Hello,

How are you generating your Z data?  This data has to be dependent on the other two variable in some way. Also, notice that both the Y array and the X array have to be formatted as instructed in the help file (see attached VI)

In general, having uneven spaced data is not a limitation.  However, if you provide more information regarding the way by which you are creating your Z array, I should be able to further help with this issue.

Regards,

AG

[AG123]

didn't save values.. this VI's better 🙂

AG

[vituning]

AG -

Thanks for the VI. I do understand that the X and Y data need to be monotonically increasing and formatted as a mesh as you showed me in your VI. However, the problem I run into is when generating the Z matrix. I have scattered points that have been measured in different X and Y locations, and do not represent a regular 2D grid. Sometimes the data is measured in a few points around a circle, for instance, but I want to interpolate over a rectangle containing the circle.

So, my Z data looks like this (see attached image):

Which I can write as a 1-D array into the griddata function in matlab

[AG123]

Hello,

I am in the process of discussing this issue with R&D.  They are aware of the difficulty such a problem creates, and should get back with me soon.  I will let you know either way as soon as I hear back.

Thanks for your patience,

AG,

National instruments

[vituning]

AG -

I appreciate you taking the time to look into this. Right now, I'm using the Matlab node to run griddata in my LV code. Of course, I would rather have a way to do it in 100% LabVIEW (without writing my own griddata function).

thanks.

[AG123]

I understand.  I'll get back with you as soon as I have something.

Have a good weekend! 🙂

[AG123]

Good News!

Our R&D department has created this functionality in LabVIEW 8.20!  However, there are some issues associated with its help and documentation.  To fix these issues, please refer to the following link: http://digital.ni.com/public.nsf/allkb/d97af9ecd0236d6f862571d9005ea79f

If you have LabVIEW 8.0 and would like assistance executing the griddata function with it, please contact our technical support department via email by going to the following link: http://sine.ni.com/apps/utf8/nicc.call_me

I hope this helps, and apologize for the delayed response.

Best of luck,

AG, National Instruments

[vituning]

Wow, thanks for the response. I have 8.2, and I didn't notice griddata in the list of new functions supported by the Mathscript node. I'm not too worried about the help, since I am already using the MATL version of griddata in 8.0. I'll try it out and let you know how it works.

Thanks again, great support.

[chilly_charly]

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vituning a écrit: ... I'm not too worried about the help, since I am already using the MATL version of griddata in 8.0. I'll try it out and let you know how it works.

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Well, I'm not using MatLab and some help would be strongly appreciated ! Could you post an example ?