On Wed, Aug 14, 2019 at 5:37 PM Hans Hagen wrote:

On 8/14/2019 4:58 PM, Mikael P. Sundqvist wrote:

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1) 3d support. This is of course a very big request, but it would also be useful for many people.

yes ... Alan and I are thinking of some (not that we came far yet)

Please keep us updated! :)

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2) About graphing, it would be nice to be able to do contour polots and density plots. I know I asked for contour plots some time ago, and there were some examples, but I don't think there was ever some built in support for it. Maybe that can be done "easy" with help of lua? I guess there exist good algorithms.

spec needed ... as 'code' can be any function it's mostly a matter of what to pipe back to mp

I'm not sure what kind of spec you need. What I have in mind (others could complete) is in particular a way to plot the set of (x,y) such that f(x,y)=0 for some given function f and some rectangle in x and y. I made some plots with Mathematica http://www.maths.lth.se/matematiklth/personal/mickep/Contour.pdf (too big for the list) The first plot shows a difficulty with a contour plot, namely intersections. In the second one I added points, and it looks better. In the third plot I have not specified that the expression should be equal to 0. Then Mathematica plots the curves f(x,y)=C for various values of C. In the background it adds a density plot (i.e. a mesh with different colours for different values of the function. In the fourth plot, the regionplot, the pairs (x,y) for which f(x,y)<0 are marked. This is also very useful. In the fifth plot there is only the densityplot, with different colors for different values of f. I don't know how difficult it is to implement this kind of graphics. Also, it could be useful to be able to input the equation f(x,y)=0 and to receive the curves as MetaPost paths. It seems that one can do contour plots with the help of lua if that is something that helps ( http://franko.github.io/graph-toolkit/contour.html). Anything would be better than nothing, and I'm more than happy to test.

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3) (small) The possibility to have arrows in coordinate axes. I have not had the possibility to test the new features today, and maybe this is already built in (drawarrow?), but I mention it since I did not see it in the pdf.

no, but that is rather trivial to add

Good!

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Again, it is very nice that you work on extending MetaPost/MetaFun further!! wel, mp is ... fun (and these extension are somewhat challenging)

Hans

Fun, indeed! /Mikael