plotting a surface defined in a domail

Francesco

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Mar 9, 2018, 6:24:50 AM3/9/18

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How can i plotting a function of two variables defined in a domain different from a square ?
I need, for example, to plot a f(x,y) where x is between 0 and 1, and y is between 0 and x ( it is a triangle )
Can you help me?

Emmanuel Charpentier

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Mar 11, 2018, 3:39:51 AM3/11/18

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A couple of ideas :

Parametric plot3d, using a convenient transformation of the parameters
implicit_plot3d
list_plot3d

Also, it might help to note that in a 3D plot, points returned as float("NA") do not plot ; however, this is undocumented and I still do not know how this is obtained. Given the changes currently undergoing in the graphics functions, you might want to use this only as a last-resort measure...

--
Emmanuel Charpentier

slelievre

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Mar 11, 2018, 12:05:39 PM3/11/18

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Building on Emmanuel Charpentier's tips, here is an example.

sage: x_range = (0, 1)

sage: y_range = (0, 1)

sage: in_domain = lambda x, y: 0 < y < x < 1

sage: def f(x, y):

....: if in_domain(x, y):

....: return x^2 + y^2

....: return float('nan')

....:

sage: plot3d(f, x_range, y_range)

sage: plot3d(f, x_range, y_range, viewer="threejs")

Francesco

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Mar 14, 2018, 9:22:44 AM3/14/18

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thank you Charpentier and Slelievre;
I have an other question: the command

plot3d(f, x_range, y_range, viewer="threejs")

doesn't plot the surface but only the edges of a box . How can i install this viewer ?

slelievre

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Mar 14, 2018, 9:29:25 AM3/14/18

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Wed 2018-03-14 13:22:44 UTC, Francesco:

> I have an other question: the command
> plot3d(f, x_range, y_range, viewer="threejs")

> doesn't plot the surface but only the edges of a box. How can i install this viewer?