From: Alan W. Irwin <irwin@be...>  20050325 16:10:21

On 20050325 13:21+0100 Arjen Markus wrote: > Curtis Cooper wrote: >> >>> Hi, >>> >>> I'm using PLplot to produce pictures of longitude, latitude temperature >>> maps for my planetary atmospheres research. I first apply an orthographic >>> projection to the lon, lat coordinates and use the grid so computed as the >>> argument into plshades along with pltr2: >>> >>> plshades(temperature, clevels, fill_width, 0, pltr2, X, Y, 2) >>> >>> Temperature here is known at all longitudes and latitudes for which I have >>> computed the X,Y projection matrices, i.e., T(lon, lat). >>> >>> This is just like example 16. Now, the routine plots the map projection >>> beautifully. However, for further computations, I would really like to be >>> able to extract the projected data, i.e., T in the X,Y coordinate system. >>> What would be involved in modifying the PLplot source code to allow me to >>> do that? >>> > > Nothing: > > The function pltr2() is doing the actual coordinate transformation. You > can > call it yourself like this: > > for (i = 0; i < n; i++) { > pltr2 (x[i], y[i], &tx, &ty, pltr_data); > x[i] = tx; > y[i] = ty; > } > > where pltr_data is the grid matrix. It may not be much further help beyond what Arjen has already said, but sparse documentation of pltr2 actually exists at http://plplot.sourceforge.net/docbookmanual/plplothtml5.3.1/pltr2.html . Alan __________________________ Alan W. Irwin email: irwin@... phone: 2507272902 Astronomical research affiliation with Department of Physics and Astronomy, University of Victoria (astrowww.phys.uvic.ca). Programming affiliations with the FreeEOS equationofstate implementation for stellar interiors (freeeos.sf.net); PLplot scientific plotting software package (plplot.org); the Yorick frontend to PLplot (yplot.sf.net); the Loads of Linux Links project (loll.sf.net); and the Linux Brochure Project (lbproject.sf.net). __________________________ Linuxpowered Science __________________________ 