It is easy to see why the plot is off for n<4, by looking at the
implementation:
sage: graphs.WheelGraph??
the plotting layout is computed in the 1st 6 lines of the implementation:
pos_dict = {}
pos_dict[0] = (0,0)
for i in range(1,n):
x = float(cos((pi/2) + ((2*pi)/(n-1))*(i-1)))
y = float(sin((pi/2) + ((2*pi)/(n-1))*(i-1)))
pos_dict[i] = (x,y)
and it's all good for n>3, but for n<4 it's certainly not.
I've opened https://trac.sagemath.org/ticket/24512 to fix this.
On Thursday, January 11, 2018 at 3:37:46 AM UTC, 漂 wrote:
>
> sage: graphs.WheelGraph(3).is_isomorphic(graphs.CompleteGraph(3))
> True
> But graphs.WheelGraph(3).show()
>
>
> <https://lh3.googleusercontent.com/-iKLcJ9btZ1I/WlbbWONcvtI/AAAAAAAAMvQ/92jJW86d-n0eQUCTaZoqDZpwnO3eV3vDgCLcBGAs/s1600/sage.png>
> show(Graph(graphs.WheelGraph(3).edges())) is OK.
> So I do not know why.
>
>
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