Useful Sage and phase portraits resource

[kcrisman]

I found this resource online - anyone know of other good ones for phase portraits?
http://www.ms.uky.edu/~ma138/Spring16/Sage_instruction.pdf

[Henri Girard]

Yes mine :)
It's a work from a french lycee in py but I have convert it in sage and julia they are oriented RLC circuits.
https://github.com/aishenri/julexample, that's the julia part, but I can load sagemath ipynb if you want ?

[Thierry]

On Mon, Aug 22, 2016 at 01:45:05AM -0700, Henri Girard wrote:
> Yes mine :)
> It's a work from a french lycee in py but I have convert it in sage and
> julia they are oriented RLC circuits.
> https://github.com/aishenri/julexample, that's the julia part, but I can
> load sagemath ipynb if you want ?

Definitely !

Ciao,
Thierry

> Le mercredi 4 mai 2016 14:52:30 UTC+2, kcrisman a écrit :
> >
> > I found this resource online - anyone know of other good ones for phase
> > portraits?
> > http://www.ms.uky.edu/~ma138/Spring16/Sage_instruction.pdf
> >
>

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[slelievre]

2016-05-04 14:52:30 UTC+2, kcrisman wrote on sage-edu:

> I found this resource online - anyone know of other good ones for phase portraits?

> http://www.ms.uky.edu/~ma138/Spring16/Sage_instruction.pdf

There are also interesting examples at

  https://wiki.sagemath.org/interact/diffeq

[魏华祎]

Hi, guys,

I define `g1` and `g2` in the following code, but I am not so clear about their difference. Hope you guys show me some clues about it. Thanks very much.

```

var('t')

g1=4*t^2 + 3*t + 1

g2(t)=4*t^2 + 3*t +1

```

Best 

Huayi 

[David Joyner]

sage: var('t')
t
sage: g1=4*t^2 + 3*t + 1
sage: g2(t)=4*t^2 + 3*t +1
sage: g1(2)
/Users/wdj/sagefiles/SageMath/local/lib/python2.7/site-packages/IPython/core/interactiveshell.py:2885:
DeprecationWarning: Substitution using function-call syntax and
unnamed arguments is deprecated and will be removed from a future
release of Sage; you can use named arguments instead, like EXPR(x=...,
y=...)
See http://trac.sagemath.org/5930 for details.
exec(code_obj, self.user_global_ns, self.user_ns)
23
sage: g1(t=2)
23
sage: g2(2)
23

Does that help?

>
> Best
>
> Huayi

[Wei, Huayi]

Hi, David,

Thanks for your reply.

so `g1` is a expression and `g2` is a function.

And `g1(t=2)` is a substitution and `g2(2)` is a function call.

Have I understood correctly?

Best

Huayi

[David Joyner]

On Thu, Aug 25, 2016 at 10:14 AM, Wei, Huayi <weih...@xtu.edu.cn> wrote:
> Hi, David,
>
> Thanks for your reply.
>
> so `g1` is a expression and `g2` is a function.
>
> And `g1(t=2)` is a substitution and `g2(2)` is a function call.
>
> Have I understood correctly?
>

Yes.

[Wei, Huayi]

Hi, Guys,

I solve an ode and get an implicit solution as following, and my
question is how to plot `f` by `implicit_plot` command.

```

var('t')

y = function('y')(t)

de = diff(y, t)/((2-y)*y) == 1

f = desolve(de, y, [0, 10]) # the solution is -1/2*log(y(t) - 2) +
1/2*log(y(t)) == t + 1/2*log(10) - 1/2*log(8)
```

Thanks

Huayi

[slelievre]

Huayi,

To ask a new question on sage-edu, do one of these:

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DO NOT "reply to" a post on an unrelated topic.

Regards,

Samuel

[David Joyner]

sage: var("t,y")
(t, y)
sage: implicit_plot(-1/2*log(y - 2) + 1/2*log(y) == t + 1/2*log(10) -
1/2*log(8), (t, 0, 2), (y, 2.1,10), figsize=4, axes="true" )

worked for me.

For more info on the syntax, see here

http://doc.sagemath.org/html/en/reference/plotting/sage/plot/contour_plot.html#sage.plot.contour_plot.implicit_plot

and also here

http://sagemath.wikispaces.com/implicit_plot

> Thanks

[Wei, Huayi]

Hi, David,

You code also worked for me. Thanks.

Best

Huayi

[Henri Girard]

Happy New Year

Here there is a pure sagemath graphic about RLC (angular pulsation and resonance frequency)
I am working on how to make them looking better

https://github.com/aishenri/sage/blob/master/rlc-graph-rad-hz.ipynb