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cougar2
Germany
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 Posted - 01/09/2004 : 05:13:08 AM
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Hi everyone,
I have 20 2d plots which are taken at a different angle each (0-360). Now I am plotting those 20 graphs into one 3d graph giving me something (but not quite) like a surface (only scatter points). I would like to do a real surface plot (with interpolated points in between). However, I have difficulties in converting my worksheet into a matrix, because I calculate the x and y values for each angle (with radius*cos(phi), radius*sin(phi)) and then have z values for each of those x,y pairs (and this 20 times). So my worksheet has 3 columns for each 2d graph.
Can anybody help in setting up the matrix? It would be something like a 3d polar plot.
Thanks
Cougar
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edgar.kaiser
Switzerland
29 Posts |
Posted - 01/14/2004 : 05:58:38 AM
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Hi Cougar,
you need to perform a so called gridding procedure. You can concatenate all your 20 xyz datasheets into one data sheet with 3 columns (xyz). Then perform one of the built-in gridding procedures. I guess you will need a random gridding procedure, because from your description, your xy data will not fit into a regularly spaced grid.
You find this in EDIT -> Convert to matrix -> random xyz.
Random gridding takes the input xyz data and calculates interpolated xyz data fitting into a regular xy grid, which is required to set up the matrix. Several procedures are available. Which one is the best depends on the characteristics of your input data.
You will need some trial and error efforts to elaborate the procedure. It is not trivial.
If your data is noisy, interpolation will not give a good smooth surface. In this case you should consider a gridding procedure that fits a model surface (e.g. 2D-B-splines) by a non-linear least-squares-fitting procedure. This is not built-in to Origin. But Origin C has NAG library functions to do that.
Best regards,
Edgar
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3d plot from 2d plots at different angles