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tommeh!!
UK
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 Posted - 09/27/2004 : 11:11:27 AM
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Hiya, hope this hasn't been asked before, couldn't seem to find anything similar!!!
I've got some measured data in r, theta and z that i'd like to plot as a 3D surface. I can convert this to x, y and z in excel, but am having issues in the plotting of the graph, I think due to the small amount of data I have.
If I choose the "sparse matrix" option, Origin seems to discount some of the points, and then plots a series of spikes. If I try to convert the data to a matrix using the "random XYZ" option it seems to smooth out or change some of the points.
Is there a way of just interpolating between the data points??? even just straight lines would give a workable solution.
Many thanks,
tom
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easwar
USA
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Posted - 09/28/2004 : 10:02:07 AM
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Hi Tom,
Looks like what you have is random XYZ data - that is to say, the X, Y values do not have equal spacing.
Currently then the only available way of plotting such data as a grid is to first perform gridding on the random data to create a surface/matrix. There are five different gridding methods including two from the NAG library. All of these may create grids that do not go thru your data points, but are representative of the data, and so they can end up "smoothing" the data in essense, which is what you are seeing.
We do not currently have a 3D Spline surface generation capability which is what I think you want - be able to see the surface go thru all the data points. We will consider adding such in the future.
As for sparse matrix conversion, that also assumes regular spacing in x, y - just that some x,y pairs would be missing in the data. So if the data has random spacing in x,y then sparse is not suitable.
Thanks,
Easwar
OriginLab
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tommeh!!
UK
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Posted - 09/28/2004 : 10:32:25 AM
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Hi Easwar,
Thanks for the quick response, a 3D spline surface would be ideal, but i guess i might be able to have a try at writing a spreadsheet which could simulate a straight line between points to increase the amount of data, which may then get round the problem.....
Cheers for the advice,
tom
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3D Surface Plot