Opened 12 years ago
Last modified 6 years ago
#11225 new defect
improve piecewise plotting
Reported by: | Karl-Dieter Crisman | Owned by: | jason, was |
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Priority: | major | Milestone: | sage-7.3 |
Component: | graphics | Keywords: | piecewise |
Cc: | David Joyner, Jason Grout, Robert Pollak, Karl-Dieter Crisman, Volker Braun, Samuel Lelièvre, Matthias Köppe, Eviatar Bach, Ralf Stephan | Merged in: | |
Authors: | Reviewers: | ||
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | #14801 | Stopgaps: |
Description (last modified by )
Until we actually totally rewrite piecewise functions (done in #14801), we should improve some things.
For concreteness, here is one thing that should work but doesn't. I'm sure there are more - add to this list, and then whatever isn't fixed in this ticket can be moved to another ticket. I just want to make sure they're listed in one place, not ten tickets.
List:
- plotting more than one
sage: f = Piecewise([[(0,1),x^3], [(1,2),x^2]], x) sage: plot([f,x^3],(x,0,2))
A very similar example was at this ask.sagemath.org post:sage: f = Piecewise([[(-2,1),1],[(1,4),x]]) sage: g = Piecewise([[(-2,1),1],[(1,4),2*x]]) sage: plot([f,g]) AttributeError: PiecewisePolynomial instance has no attribute '__float__'
Both examples work in the new
piecewise
(#14801):sage: f = piecewise([[(0,1),x^3], [(1,2),x^2]], var=x) sage: plot([f,x^3],(x,0,2))sage: f = piecewise([[(-2,1),1],[(1,4),x]]) sage: g = piecewise([[(-2,1),1],[(1,4),2*x]]) sage: plot([f,g], xmin=-3, xmax=5)
- plotting a product of a piecewise with a symbolic (well, the problem is multiplying the two, but still worth putting here - see this sage-support thread)
fixed in new
piecewise
- Maybe unify with
plot_step_function
, which currently is sort of its own thing? - In this example:
sage: zero_func(x)=0 sage: g = Piecewise([[(-1000,1),zero_func],[(1,1000),(x-1)^3]],x) sage: G = g.plot() sage: G.show(xmin=-5,xmax=5,ymax=100) sage: g(1) 0
- You can use oo (infinity) for endpoints, but then the plot code for Piecewise gets screwed up.
- You can try putting in zero instead of defining this new zero function, but then g(1) and g(-1) etc. won't work.
- You can try using extend_by_zero to make the zero part, but it gives the same problem.
- You can plot without xmin and xmax, but that gives the whole function.
- You can plot without ymax, but that gives the range further out than you want.
- You can try plot(g), but that turns out to uncover a very strange error that may or may not be a bug.
In new
piecewise
(#14801) 0 is no longer in the domain (open intervals?); and there is now support for unbounded intervals.sage: zero_func(x)=0 sage: g = piecewise([[(-1000,1),zero_func],[(1,1000),(x-1)^3]]) sage: G = g.plot() sage: G.show(xmin=-5,xmax=5,ymax=100) Launched png viewer for Graphics object consisting of 1 graphics primitive sage: g(1) ValueError: point 1 is not in the domain
See also #1773.
Change History (12)
comment:1 Changed 12 years ago by
Description: | modified (diff) |
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comment:2 Changed 12 years ago by
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comment:3 Changed 11 years ago by
Description: | modified (diff) |
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comment:4 Changed 11 years ago by
Description: | modified (diff) |
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comment:5 Changed 11 years ago by
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comment:6 Changed 11 years ago by
Description: | modified (diff) |
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comment:7 Changed 11 years ago by
From DSM on this ask.sagemath.org question:
# monkeypatch legend duplication of trac #11225 def fix_piecewise(fn): import types def fixed_plot(self, *args, **kwargs): from sage.plot.all import plot return sum([plot(f, a, b, *args, **(dict((k,v) for k,v in kwargs.items() if i == 0 or k != 'legend_label'))) for i, ((a,b),f) in enumerate(self.list())]) def fn2(*args, **kwargs): ans = fn(*args, **kwargs) ans.plot = types.MethodType(fixed_plot, ans) return ans return fn2 Piecewise = fix_piecewise(Piecewise)
Nice protopatch, perhaps?
comment:8 Changed 11 years ago by
Description: | modified (diff) |
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I removed the last bullet point and created #12651 where I'll post a patch with dsm's fix.
comment:9 Changed 9 years ago by
Cc: | Robert Pollak added |
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comment:10 Changed 9 years ago by
Dependencies: | → #14801 |
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comment:11 Changed 6 years ago by
Cc: | Karl-Dieter Crisman Volker Braun Samuel Lelièvre Matthias Köppe Eviatar Bach Ralf Stephan added |
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Description: | modified (diff) |
Keywords: | piecewise added |
Updated description for new piecewise
(#14801).
Didn't check the xmin/xmax etc. behavior that is mentioned in the description.
This can probably be closed when the old Piecewise
(now deprecated) is removed completely.
comment:12 Changed 6 years ago by
Milestone: | → sage-7.3 |
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Regarding the first item (can't plot two of them), It probably wouldn't even be that hard to fix. The problem is that
setup_for_eval_on_grid
wants to usefast_float
butPiecewise
guys don't have that, or more precisely don't have__float__
.